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NXLog Documentation

Windows DNS Server

Windows DNS Server is a Windows server role which acts as the Global Catalog server for the forest and domain within Active Directory. DNS logging is an essential part of security monitoring.

NXLog can be configured to collect Windows DNS logging data from various sources such as ETW providers, log files, Sysmon, and Windows Event Log.

Windows DNS monitoring overview

NXLog offers four general event logging facilities for monitoring DNS events generated by Windows DNS Server and its clients:

The following table maps some of the key features and attributes unique to each NXLog logging facility available for Windows DNS monitoring.

Table 1. Windows DNS monitoring overview
DNS Logging or Tracing Type Provider or Channel Module(s) Feature(s) Requirements

Audit and Analytical
(Tracing)

Microsoft-Windows-DNSServer

im_etw

Preferred method.
Native DNS Server auditing.
Best choice for Analytical logs.

Server versions 2012 R2 and later

Debug
(Logging,
Details option disabled)

im_file
xm_msdns

Fast.
The only way to log DNS transaction information.

Windows Server versions 2008 R2, 2012 R2, and 2016

Debug
(Logging,
Details option enabled)

im_file
xm_multiline

Fast.
The only way to log DNS transaction information.

Active Directory auditing
(Logging)

Microsoft-Windows-Security-Auditing

im_msvistalog

Systems without native DNS auditing

Windows 8.1 or later

Native DNS auditing
(Logging)

Microsoft-Windows-DNSServer/Audit

im_msvistalog

Preferred method for collecting DNS audit logs

Windows Server 2016, or 2012 R2 with hotfix 2956577

Sysmon
(Logging or Tracing)

Microsoft-Windows-Sysmon/Operational
Sysmon Event ID 22

im_msvistalog

Only DNS client query logging, but it is the only way to obtain the name and path of the client application executing the query.

Windows 8.1 or later
Sysmon v10.0 or later

DNS Client
(Logging or Tracing)

Microsoft-Windows-DNS-Client/Operational

im_msvistalog

Another source of DNS client query logging.

Windows 8.1 or later

DNS logging via ETW providers

Enhanced Windows DNS Event Log logging is available from Event Tracing for Windows providers. There are two event categories:

  1. Windows DNS Server Audit Events are enabled by default. An audit event is logged whenever the DNS Server settings, zones, or resource records are changed. Such DNS events are of utmost importance for security audits. Each of the 53 audit event types is identified by a unique EventID documented in the Audit events table of Microsoft’s documentation. The Type column in this table contains a short description of the event; however, it is not included in the actual logged event. For example, if a new zone is created, it will not be possible to search for an event containing Record create. Instead, only EventID: 515 is available for identifying this type of event.

  2. Windows DNS Server Analytical Events must be specifically enabled. They represent the bulk of DNS events—​primarily lookups and other queries—​and can be quite large in volume. The Analytic events table of Microsoft’s documentation lists each of the 23 types of events that are monitored. Just like with Audit Events, Windows logs the EventID, but not the more descriptive Type field. According to the Audit and analytic event logging section of Microsoft’s documentation, when processing 100,000 queries per second (QPS) on modern hardware, the expected reduction in performance is around 5% if Analytical Event logging is enabled.

Event tracing offers significant advantages over DNS Debug Logging in terms of architecture, flexibility, configurability, and performance. ETW events can be read directly without requiring events to be first written to disk. However, ETW is not available on older Windows systems. To maintain its performance, it is by design a "best effort" framework and consequently does not guarantee that all events will be captured.

For more information, see the Installing and enabling DNS diagnostic logging section on Microsoft Docs.

With Analytical Logging enabled, NXLog can use the im_etw module to collect DNS logs from the Microsoft-Windows-DNSServer ETW provider. This is the preferred method for collecting logs from Windows Server versions 2012 R2 and later.

On Windows Server 2012 R2, this feature is provided by hotfix 2956577.

Examples

Example 1. Using im_etw

The following configuration collects DNS logs via ETW from the Microsoft-Windows-DNSServer provider using the im_etw module. The collected logs are converted to JSON with the to_json() procedure of the xm_json module.

nxlog.conf
<Extension _json>
    Module      xm_json
</Extension>

<Input etw>
    Module      im_etw
    Provider    Microsoft-Windows-DNSServer
    Exec        to_json();
</Input>
Output sample of Audit EventID: 515, identifying creation of a new record in the zone example.com
{
  "SourceName": "Microsoft-Windows-DNSServer",
  "ProviderGuid": "{EB79061A-A566-4698-9119-3ED2807060E7}",
  "EventID": 515,
  "Version": 0,
  "ChannelID": 17,
  "OpcodeValue": 0,
  "TaskValue": 5,
  "Keywords": "4611686018428436480",
  "EventTime": "2020-03-10T09:42:39.788511-07:00",
  "ExecutionProcessID": 4752,
  "ExecutionThreadID": 1732,
  "EventType": "INFO",
  "SeverityValue": 2,
  "Severity": "INFO",
  "Domain": "WIN-R4QHULN6KLH",
  "AccountName": "Administrator",
  "UserID": "S-1-5-21-915329490-2962477901-227355065-500",
  "AccountType": "User",
  "Flags": "EXTENDED_INFO|IS_64_BIT_HEADER|PROCESSOR_INDEX (577)",
  "Type": "1",
  "NAME": "www.example.com",
  "TTL": "3600",
  "BufferSize": "4",
  "RDATA": "0x0A00020F",
  "Zone": "example.com",
  "ZoneScope": "Default",
  "VirtualizationID": ".",
  "EventReceivedTime": "2020-03-10T09:42:40.801598-07:00",
  "SourceModuleName": "etw",
  "SourceModuleType": "im_etw"
}

File-based DNS debug logging

Windows DNS debug logging is the only means of monitoring DNS events on Windows Server versions before 2012 R2. However, DNS Servers capable of ETW might be configured for file-based logging in cases where all events must be captured without exception.

Enabling DNS debug logging

Follow these steps to enable DNS debug logging:

  1. Open the DNS Management console (dnsmgmt.msc).

  2. Right-click on the DNS Server and choose Properties from the context menu.

  3. Under the Debug Logging tab, enable Log packets for debugging.

    DNS Server Properties window
    Figure 1. DNS Server Properties window

  4. Select the checkboxes corresponding to the data that should be logged.

    The Details option will produce multi-line logs. To parse this detailed format, refer to Parsing detailed DNS logs with regular expressions below.

  5. Set the File path and name to the desired log file location.

    The Windows DNS service may not recreate the debug log file after a rollover. If you encounter this issue, use the C: drive for the debug log path. See The disappearing Windows DNS debug log on the NXLog blog.
Log sample (standard debug mode, one query per line)
4/21/2017 7:52:03 AM 06B0 PACKET  00000000028657F0 UDP Snd 10.2.0.1        6590 R Q [8081   DR  NOERROR] A      (7)example(3)com(0)

Parsing non-detailed logs with xm_msdns

The xm_msdns module, available in NXLog Enterprise Edition, can parse Windows DNS Server logs.

This module does not support parsing DNS logs in the detailed debug logging format. See Parsing detailed DNS logs with regular expressions.
This module has been tested on Windows Server versions 2008 R2, 2012 R2, and 2016.
Example 2. Parsing DNS logs with xm_msdns

This configuration uses the im_file and xm_msdns modules to read and parse the DNS debug log file. The collected logs are converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
<Extension json>
    Module       xm_json
</Extension>

<Extension dns_parser>
    Module       xm_msdns
    EventLine    TRUE
    PacketLine   TRUE
    NoteLine     TRUE
</Extension>

<Input dns_logs>
    Module       im_file
    File         'C:\Server\dns.log'
    InputType    dns_parser
    Exec         to_json();
</Input>
Output sample
{
  "EventTime": "2022-09-20 07:52:03",
  "ThreadId": "06B0",
  "Context": "PACKET",
  "InternalPacketIdentifier": "00000000028657F0",
  "Protocol": "UDP",
  "SendReceiveIndicator": "Snd",
  "RemoteIP": "10.2.0.1",
  "Xid": "6590",
  "QueryResponseIndicator": "Response",
  "Opcode": "Standard Query",
  "FlagsHex": "8081",
  "RecursionDesired": true,
  "RecursionAvailable": true,
  "ResponseCode": "NOERROR",
  "QuestionType": "A",
  "QuestionName": "example.com",
  "EventReceivedTime": "2022-09-20 7:52:03",
  "SourceModuleName": "dns_logs",
  "SourceModuleType": "im_file"
}

Parsing non-detailed logs with regular expressions

While the xm_msdns module is the preferred method and is about three times faster, you can also use regular expressions to parse DNS debug logs.

This example does not parse DNS logs in the detailed debug logging format. See Parsing detailed DNS logs with regular expressions.
This example has been tested on Windows Server versions 2008 R2, 2012 R2, and 2016.
Example 3. Parsing DNS logs with regular expressions

This configuration collects DNS debug logs using the im_file input module and parses them with regular expressions. The collected logs are converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
define EVENT_REGEX /(?x)(?<Date>\d+(?:\/\d+){2})\s \
                    (?<Time>\d+(?:\:\d+){2}\s\w+)\s \
                    (?<ThreadId>\w+)\s+ \
                    (?<Context>\w+)\s+ \
                    (?<InternalPacketIdentifier>[[:xdigit:]]+)\s+ \
                    (?<Protocol>\w+)\s+ \
                    (?<SendReceiveIndicator>\w+)\s \
                    (?<RemoteIP>[[:xdigit:].:]+)\s+ \
                    (?<Xid>[[:xdigit:]]+)\s \
                    (?<QueryType>\s|R)\s \
                    (?<Opcode>[A-Z]|\?)\s \
                    (?<QFlags>\[(.*?)\])\s+ \
                    (?<QuestionType>\w)\s+ \
                    (?<QuestionName>.*)/
define EMPTY_EVENT_REGEX /(^$|^\s+$)/
define DOMAIN_REGEX /\(\d+\)([\w-]+)\(\d+\)([\w-]+)/
define SUBDOMAIN_REGEX /\(\d+\)([\w-]+)\(\d+\)([\w-]+)\(\d+\)(\w+)/
define NOT_STARTING_WITH_DATE_REGEX /^(?!\d+\/\d+\/\d+).+/
define QFLAGS_REGEX /(?x)(?<FlagsHex>\d+)\s+ \
                     (?<FlagsCharCodes>\s+|([A-Z]{2}|[A-Z]))\s+ \
                     (?<ResponseCode>\w+)/

<Extension json>
    Module    xm_json
</Extension>

<Input dns_logs>
    Module    im_file
    File      'C:\Server\dns.log'
    <Exec>
        # Drop entries that have empty lines
        if $raw_event =~ %EMPTY_EVENT_REGEX% {
            drop();
        }

        # Drop entries not starting with a date
        if $raw_event =~ %NOT_STARTING_WITH_DATE_REGEX% {
            drop();
        }

        # Split entries into fields & define regular entries
        if $raw_event =~ %EVENT_REGEX% {
            $Regular = TRUE;
            $EventTime  = parsedate($Date + " " + $Time);
            $Raw = $raw_event;
            delete($date);
            delete($time);
            if $FlagsCharCodes =~ /^\s+$/ {
                delete($FlagsCharCodes );
            }

            # Convert domains from (8)mydomain(1)com to mydomain.com
            if $QuestionName =~ %DOMAIN_REGEX% {
                $QuestionName = $1 + "." + $2;
            }

            # Convert domains from (8)sub(8)mydomain(1)com to sub.mydomain.com
            if $QuestionName =~ %SUBDOMAIN_REGEX% {
                $QuestionName = $1 + "." + $2 + "." +$3;
            }

            # Set query flags
            if $QFlags =~ %QFLAGS_REGEX% {
                delete($QFlags);
            }

            # Set the query type
            if $QueryType =~ %EMPTY_EVENT_REGEX% {
                $QueryType = "query";
            }
            else {
                $QueryType = "response";
            }
        }
        else
        {
            $Regular = FALSE;
            $Raw = $raw_event;
        }

        to_json();
    </Exec>
</Input>
Output sample
{
  "EventReceivedTime": "2022-09-20 07:52:16",
  "SourceModuleName": "dns_logs",
  "SourceModuleType": "im_file",
  "Context": "PACKET",
  "InternalPacketIdentifier": "00000000028657F0",
  "Opcode": "Q",
  "Protocol": "UDP",
  "QueryType": "response",
  "QuestionName": "example.com",
  "QuestionType": "A",
  "RemoteIP": "10.2.0.1",
  "SendReceiveIndicator": "Snd",
  "ThreadId": "06B0",
  "Xid": "6590",
  "Regular": true,
  "EventTime": "2022-09-20 07:52:03",
  "Raw": "9/20/2022 7:52:03 AM 06B0 PACKET  00000000028657F0 UDP Snd 10.2.0.1        6590 R Q [8081   DR  NOERROR] A      (9)example(3)com(0)",
  "FlagsCharCodes": "DR",
  "FlagsHex": "8081",
  "ResponseCode": "NOERROR"
}

Parsing detailed DNS logs with regular expressions

Detailed DNS logging uses a multi-line format that can be parsed with xm_multiline and regular expressions.

Example 4. Parsing multi-line detailed debug DNS logs

In this example, the xm_multiline module joins lines that belong to the same event by using a regular expression to match the header line. Then another regular expression is used to parse the content into fields. The collected logs are converted to JSON using the to_json() procedure of the xm_json module.

Input sample
9/20/2022 8:33:36 PM 09B8 PACKET  0000022041EED460 UDP Rcv 192.168.56.1    edaa   Q [2001   D   NOERROR] A      (6)example(3)com(0)
UDP question info at 0000022041EED460
  Socket = 680
  Remote addr 192.168.56.1, port 48210
  Time Query=6941, Queued=0, Expire=0
  Buf length = 0x0fa0 (4000)
  Msg length = 0x0027 (39)
  Message:
    XID       0xedaa
    Flags     0x0120
      QR        0 (QUESTION)
      OPCODE    0 (QUERY)
      AA        0
      TC        0
      RD        1
      RA        0
      Z         0
      CD        0
      AD        1
      RCODE     0 (NOERROR)
nxlog.conf
define EVENT_REGEX /(?x)(?<Date>\d+(?:\/\d+){2})\s \
                   (?<Time>\d+(?:\:\d+){2}\s\w+)\s \
                   (?<ThreadId>\w+)\s+ \
                   (?<Context>\w+)\s+ \
                   (?<InternalPacketIdentifier>[[:xdigit:]]+)\s+ \
                   (?<Protocol>\w+)\s+ \
                   (?<SendReceiveIndicator>\w+)\s \
                   (?<RemoteIP>[[:xdigit:].:]+)\s+ \
                   (?<Xid>[[:xdigit:]]+)\s \
                   (?<QueryType>\s|R)\s \
                   (?<Opcode>[A-Z]|\?)\s \
                   (?<QFlags>\[(.*?)\])\s+ \
                   (?<QuestionType>\w+)\s+ \
                   (?<QuestionName>.*)\s+  \
                   (?<LogInfo>.+)\s+.+=\s \
                   (?<Socket>\d+)\s+ Remote\s+ addr\s \
                   (?<RemoteAddr>.+),\sport\s \
                   (?<PortNum>\d+)\s+Time\sQuery= \
                   (?<TimeQuery>\d+),\sQueued= \
                   (?<Queued>\d+),\sExpire= \
                   (?<Expire>\d+)\s+.+\( \
                   (?<BufLen>\d+)\)\s+.+\( \
                   (?<MsgLen>\d+)\)\s+Message:\s+ \
                   (?<Message>(?s).*)/

define HEADER_REGEX /(?x)(?<Date>\d+(?:\/\d+){2})\s \
                    (?<Time>\d+(?:\:\d+){2}\s\w+)\s \
                    (?<ThreadId>\w+)\s+ \
                    (?<Context>\w+)\s+ \
                    (?<InternalPacketIdentifier>[[:xdigit:]]+)\s+ \
                    (?<Protocol>\w+)\s+ \
                    (?<SendReceiveIndicator>\w+)\s \
                    (?<RemoteIP>[[:xdigit:].:]+)\s+ \
                    (?<Xid>[[:xdigit:]]+)\s \
                    (?<QueryType>\s|R)\s \
                    (?<Opcode>[A-Z]|\?)\s \
                    (?<QFlags>\[(.*?)\])\s+ \
                    (?<QuestionType>\w+)\s+ \
                    (?<QuestionName>.*)/

<Extension json>
    Module       xm_json
</Extension>

<Extension multiline>
    Module       xm_multiline
    HeaderLine   %HEADER_REGEX%
</Extension>

<Input dns_logs>
    Module       im_file
    File         'C:\Server\dns.log'
    InputType    multiline
    <Exec>
        if $raw_event =~ %EVENT_REGEX%
        {
            $EventTime  = parsedate($Date + " " + $Time);
            delete($Date);
            delete($Time);
            to_json();
        }
    </Exec>
</Input>
Output sample
{
  "EventReceivedTime": "2022-09-20T20:33:38.660127+01:00",
  "SourceModuleName": "dns_logs",
  "SourceModuleType": "im_file",
  "BufLen": "512",
  "Context": "PACKET",
  "Expire": "0",
  "InternalPacketIdentifier": "000000D58F45A560",
  "LogInfo": "UDP response info at 000000D58F45A560",
  "Message": "XID       0x000d\r\n    Flags     0x8180\r\n      QR        1 (RESPONSE)\r\n      OPCODE    0 (QUERY)\r\n      AA        0\r\n      TC        0\r\n      RD        1\r\n      RA        1\r\n      Z         0\r\n      CD        0\r\n      AD        0\r\n      RCODE     0 (NOERROR)\r\n    QCOUNT    1\r\n    ACOUNT    1\r\n    NSCOUNT   0\r\n    ARCOUNT   0\r\n    QUESTION SECTION:\r\n    Offset = 0x000c, RR count = 0\r\n    Name      \"(6)example(3)com(0)\"\r\n      QTYPE   AAAA (28)\r\n      QCLASS  1\r\n    ANSWER SECTION:\r\n    Offset = 0x001c, RR count = 0\r\n    Name      \"[C00C](6)example(3)com(0)\"\r\n      TYPE   AAAA  (28)\r\n      CLASS  1\r\n      TTL    26\r\n      DLEN   16\r\n      DATA   2a00:1450:400d:805::200e\r\n    AUTHORITY SECTION:\r\n      empty\r\n    ADDITIONAL SECTION:\r\n      empty\r\n",
  "MsgLen": "56",
  "Opcode": "Q",
  "PortNum": "60010",
  "Protocol": "UDP",
  "QFlags": "[8081   DR  NOERROR]",
  "QueryType": "R",
  "QuestionName": "(6)example(3)com(0)",
  "QuestionType": "AAAA",
  "Queued": "0",
  "RemoteAddr": "::1",
  "RemoteIP": "::1",
  "SendReceiveIndicator": "Snd",
  "Socket": "512",
  "ThreadId": "044C",
  "TimeQuery": "12131",
  "Xid": "000d",
  "EventTime": "2022-09-20T20:33:36.000000+01:00"
}

Collecting DNS query logs via Sysmon

Another potential source of DNS event logs is Sysmon. It is a system service and device driver which monitors system activity and logs events to Windows Event Log. See Setting up Sysmon for further details.

The DNS events logged by Sysmon are not the same as other DNS monitoring events like DNS Server Audit and Analytical logging or DNS Server debug logging. For example, Sysmon DNS query logging only logs client DNS queries. Yet, the information it supplies compliments the DNS Server Analytical logs by adding the name and path of the application querying the DNS Server. It can monitor DNS queries initiated by any network-enabled Windows client software, for instance, web browsers, FileZilla, WinSCP, ping, tracert, etc. However, Sysmon does not log direct DNS lookups done with nslookup.

Configure DNS query logging

Sysmon does not log DNS client queries by default. To enable DNS query logging, create a Sysmon configuration file in the same directory as Sysmon.exe:

config-dnsquery.xml
<Sysmon schemaversion="4.22">
  <EventFiltering>
    <DnsQuery onmatch="exclude"/>
  </EventFiltering>
</Sysmon>

Then, execute the following command to apply the new configuration:

C:\Windows> Sysmon.exe -c config-dnsquery.xml

To confirm that the new configuration has been applied, execute the following command:

C:\Windows> Sysmon.exe -c

The last few lines of output returned from Sysmon should produce the following confirmation that DNS Query logging is active:

Rule configuration (version 4.22):
 - DnsQuery              onmatch: exclude   combine rules using 'And'
You can find a good resource for configuring Sysmon to log DNS events in the sysmon-config GitHub repository. Despite sysmonconfig-export.xml being an XML file, the DNS section starting at line 885 <!--SYSMON EVENT ID 22 : DNS QUERY [DnsQuery]--> contains a good description of the configuration. It includes a complete RuleGroup example for filtering out known domains to reduce noise from ads and other sources that generate many events for harmless DNS lookups.

Once Sysmon is active and running as a service, it will log various events in addition to DNS queries. You can find the events in Windows Event Viewer under Applications and Services Log > Microsoft > Windows > Sysmon > Operational. Each event has an associated EventID. For example, Sysmon Event ID 22, DNSEvent (DNS query), is generated when a process executes a DNS query, whether the result is successful or fails, cached or not. The telemetry for this event was added for Windows 8.1 and is unavailable on Windows 7 and earlier. See the Sysmon section for more information.

Sysmon creates an ETW trace session to collect DNS events and writes the data to the Windows Event Log. You can collect these events with the im_msvistalog module. However, we recommend using the im_etw module to collect event data directly from the DNS providers to minimize computational overhead.
Example 5. Collecting Sysmon DNS query logs

This configuration uses the im_msvistalog module to collect Sysmon DNS query events from the Microsoft-Windows-Sysmon/Operational channel. The collected logs are converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
<Extension json>
    Module    xm_json
</Extension>

<Input sysmon>
    Module    im_msvistalog
    <QueryXML>
        <QueryList>
            <Query Id="0">
                <Select Path="Microsoft-Windows-Sysmon/Operational">
                    *[System[(EventID='22')]]
                </Select>
            </Query>
        </QueryList>
    </QueryXML>
    Exec      to_json();
</Input>
Output sample of a Sysmon DNS query event resulting from a ping
{
  "EventTime": "2022-09-20T15:47:43.685222+00:00",
  "Hostname": "HOST1",
  "Keywords": "9223372036854775808",
  "EventType": "INFO",
  "SeverityValue": 2,
  "Severity": "INFO",
  "EventID": 22,
  "SourceName": "Microsoft-Windows-Sysmon",
  "ProviderGuid": "{5770385F-C22A-43E0-BF4C-06F5698FFBD9}",
  "Version": 5,
  "TaskValue": 22,
  "OpcodeValue": 0,
  "RecordNumber": 9152,
  "ExecutionProcessID": 3880,
  "ExecutionThreadID": 868,
  "Channel": "Microsoft-Windows-Sysmon/Operational",
  "Domain": "NT AUTHORITY",
  "AccountName": "SYSTEM",
  "UserID": "S-1-5-18",
  "AccountType": "User",
  "Message": "Dns query:\r\nRuleName: \r\nUtcTime: 2022-09-20 15:47:43.274\r\nProcessGuid: {b3c285a4-5f1e-5db8-0000-0010c24d1d00}\r\nProcessId: 5696\r\nQueryName: example.com\r\nQueryStatus: 0\r\nQueryResults: ::ffff:93.184.216.34;\r\nImage: C:\\Windows\\System32\\PING.EXE",
  "Category": "Dns query (rule: DnsQuery)",
  "Opcode": "Info",
  "UtcTime": "2022-09-20 15:47:43.274",
  "ProcessGuid": "{b3c285a4-5f1e-5db8-0000-0010c24d1d00}",
  "ProcessId": "5696",
  "QueryName": "example.com",
  "QueryStatus": "0",
  "QueryResults": "::ffff:93.184.216.34;",
  "Image": "C:\\Windows\\System32\\PING.EXE",
  "EventReceivedTime": "2022-09-20T15:47:44.949924+00:00",
  "SourceModuleName": "sysmon",
  "SourceModuleType": "im_msvistalog"
}

Summary of DNS query fields

The fields of particular interest are the QueryName and Image fields, which provide information about the client machine’s network activity. From these fields, you can identify which site—​internal or external—​was queried and which Windows application was preparing to access that remote site.

The Message field usually contains a long string of information which NXLog will parse into the following fields:

  • UtcTime (used to create EventTime)

  • ProcessGuid

  • ProcessId

  • QueryName (the FQDN being looked up)

  • QueryStatus

  • QueryResults

  • Image (the full path and filename of the client application’s executable that performed the DNS query)

Monitoring DNS event sources using Windows Event Log

The im_msvistalog module is the most versatile input module for Windows since it can capture almost any type of event. For example, it can be used to collect DNS Server Audit events, DNS client events from Sysmon, and native DNS Client events with a single configuration.

Monitoring native DNS client events

Another source for monitoring DNS client events is the Microsoft-Windows-DNS-Client/Operational channel.

Example 6. Collecting native DNS client logs

This configuration uses the im_msvistalog module to collect DNS client events from the Microsoft-Windows-DNS-Client/Operational channel. The QueryXML block filters for select event IDs. The Exec block drops events for queries for wpad and types other than 1. The collected logs are then converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
<Extension json>
    Module    xm_json
</Extension>

<Input dns_client>
    Module    im_msvistalog
    <QueryXML>
        <QueryList>
            <Query Id="0">
                <Select Path="Microsoft-Windows-DNS-Client/Operational">
                    *[System[(EventID=3006 or EventID=3008 or
                              EventID=3010 or EventID=3018)]]
                </Select>
            </Query>
        </QueryList>
    </QueryXML>
    <Exec>
        if ($QueryName == 'wpad') OR ($QueryType != '1') {
            drop();
        }
        to_json();
    </Exec>
</Input>
Output sample
{
  "EventTime": "2022-09-20T14:40:08.809107-07:00",
  "Hostname": "WIN-R4QHULN6KLH",
  "Keywords": "9223372036854775808",
  "EventType": "INFO",
  "SeverityValue": 2,
  "Severity": "INFO",
  "EventID": 3006,
  "SourceName": "Microsoft-Windows-DNS-Client",
  "ProviderGuid": "{1C95126E-7EEA-49A9-A3FE-A378B03DDB4D}",
  "Version": 0,
  "TaskValue": 0,
  "OpcodeValue": 0,
  "RecordNumber": 42095,
  "ExecutionProcessID": 2224,
  "ExecutionThreadID": 4672,
  "Channel": "Microsoft-Windows-DNS-Client/Operational",
  "Domain": "WIN-R4QHULN6KLH",
  "AccountName": "Administrator",
  "UserID": "S-1-5-21-915329490-2962477901-227355065-500",
  "AccountType": "User",
  "Message": "DNS query is called for the name ntp.msn.com, type 1, query options 140738562228224, Server List , isNetwork query 0, network index 0, interface index 0, is asynchronous query 0",
  "Opcode": "Info",
  "QueryName": "ntp.msn.com",
  "QueryType": "1",
  "QueryOptions": "140738562228224",
  "IsNetworkQuery": "0",
  "NetworkQueryIndex": "0",
  "InterfaceIndex": "0",
  "IsAsyncQuery": "0",
  "EventReceivedTime": "2022-09-20T14:40:10.674875-07:00",
  "SourceModuleName": "dns_client",
  "SourceModuleType": "im_msvistalog"
}

Monitoring DNS Server audit events

Although the im_msvistalog module can collect DNS Server audit events, using im_etw is a better choice when performance is a concern and remains the recommended method.

Example 7. Collecting DNS Server audit logs

This configuration uses the im_msvistalog module to collect DNS audit events from the Microsoft-Windows-DNSServer/Audit channel. It collects all audit events since most are important, and audit logs tend to be much lower in volume than analytical or debug logs. The events are converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
<Extension json>
    Module    xm_json
</Extension>

<Input dns_audit>
    Module    im_msvistalog
    <QueryXML>
        <QueryList>
            <Query Id="0">
                <Select Path="Microsoft-Windows-DNSServer/Audit">*</Select>
            </Query>
        </QueryList>
    </QueryXML>
    Exec      to_json();
</Input>
Output sample
{
  "EventTime": "2022-09-20T14:56:07.622472-07:00",
  "Hostname": "WIN-R4QHULN6KLH",
  "Keywords": "4611686018428436480",
  "EventType": "INFO",
  "SeverityValue": 2,
  "Severity": "INFO",
  "EventID": 516,
  "SourceName": "Microsoft-Windows-DNSServer",
  "ProviderGuid": "{EB79061A-A566-4698-9119-3ED2807060E7}",
  "Version": 0,
  "TaskValue": 5,
  "OpcodeValue": 0,
  "RecordNumber": 98,
  "ExecutionProcessID": 2000,
  "ExecutionThreadID": 4652,
  "Channel": "Microsoft-Windows-DNSServer/Audit",
  "Domain": "WIN-R4QHULN6KLH",
  "AccountName": "Administrator",
  "UserID": "S-1-5-21-915329490-2962477901-227355065-500",
  "AccountType": "User",
  "Message": "A resource record of type 1, name ns2.example.com and RDATA 0x0A000210 was deleted from scope Default of zone example.com.",
  "Category": "ZONE_OP",
  "Opcode": "Info",
  "Type": "1",
  "NAME": "ns2.example.com",
  "TTL": "0",
  "BufferSize": "4",
  "RDATA": "0A000210",
  "Zone": "example.com",
  "ZoneScope": "Default",
  "VirtualizationID": ".",
  "EventReceivedTime": "2022-09-20T14:56:09.343045-07:00",
  "SourceModuleName": "dns_audit",
  "SourceModuleType": "im_msvistalog"
}

Processing DNS Server analytical events

One limitation of the im_msvistalog module is that it cannot read event traces of analytical sources. For this reason, the im_etw module remains the preferred choice for collecting events from the DNS Server Analytical log. It is possible to leverage the File directive in im_msvistalog to read DNS Server Analytical logs from .etl files. The active DNS Server Analytical log file is located at:

%SystemRoot%\System32\Winevt\Logs\Microsoft-Windows-DNSServer%4Analytical.etl

A limitation of reading .etl files with im_msvistalog is that the module cannot seek in such files, resulting in the file being read from the beginning every time NXLog is started. Therefore, you should only use this method to process DNS Server analytical logs in archived .etl files and not monitor active .etl files.

Example 8. Collecting DNS Server analytical logs

This example uses the im_msvistalog module to collect DNS analytical events.

Analytical log sources, like debug log sources, tend to generate a high volume of events that are not always useful. In this configuration, an analysis of the log file determined that frequent lookups on ten specific hosts were responsible for a sizable portion of the log file. Since none of these hosts are of interest for security monitoring, the configuration filters them out to reduce noise.

The collected logs are converted to JSON using the to_json() procedure of the xm_json module.

nxlog.conf
<Extension json>
    Module    xm_json
</Extension>

<Input dns_analytical>
    Module    im_msvistalog
    File      C:\temp\DNSServer%4Analytical-Archive.etl
    <Exec>
        if ($QNAME == 'americas1.notify.windows.com.akadns.net.') OR \
           ($QNAME == 'cy2.vortex.data.microsoft.com.akadns.net.') OR \
           ($QNAME == 'dm3p.wns.notify.windows.com.akadns.net.') OR \
           ($QNAME == 'geo.vortex.data.microsoft.com.akadns.net.') OR \
           ($QNAME == 'v10-win.vortex.data.microsoft.com.akadns.net.') OR \
           ($QNAME == 'v10-win.vortex.data.microsoft.com.akadns.NET.') OR \
           ($QNAME == 'v10.vortex-win.data.microsoft.com.') OR \
           ($QNAME == 'wns.notify.windows.com.akadns.net.') OR \
           ($QNAME == 'wns.notify.windows.com.akadns.NET.') OR \
           ($QNAME == 'client.wns.windows.com.') OR \
           ($QTYPE == '15') {
            drop();
        }
        to_json();
    </Exec>
</Input>
Output sample
{
  "EventTime": "2022-09-20T19:21:47.052133-07:00",
  "Hostname": "WIN-R4QHULN6KLH",
  "Keywords": "9223372071214514176",
  "EventType": "INFO",
  "SeverityValue": 2,
  "Severity": "INFO",
  "EventID": 279,
  "SourceName": "Microsoft-Windows-DNSServer",
  "ProviderGuid": "{EB79061A-A566-4698-9119-3ED2807060E7}",
  "Version": 0,
  "TaskValue": 1,
  "OpcodeValue": 0,
  "RecordNumber": 60,
  "ExecutionProcessID": 2000,
  "ExecutionThreadID": 4188,
  "Domain": "NT AUTHORITY",
  "AccountName": "SYSTEM",
  "UserID": "S-1-5-18",
  "AccountType": "User",
  "Message": "INTERNAL_LOOKUP_CNAME: TCP=0; InterfaceIP=10.0.2.15; Source=10.0.2.15; RD=1; QNAME=ns1.example.com.; QTYPE=1; Port=54171; Flags=34176; XID=2; PacketData=0x00028580000100010000000003777777076578616D706C6503636F6D0000010001",
  "Category": "LOOK_UP",
  "Opcode": "Info",
  "TCP": "0",
  "InterfaceIP": "10.0.2.15",
  "Source": "10.0.2.15",
  "RD": "1",
  "QNAME": "ns1.example.com.",
  "QTYPE": "1",
  "Port": "54171",
  "Flags": "34176",
  "XID": "2",
  "BufferSize": "33",
  "PacketData": "00028580000100010000000003777777076578616D706C6503636F6D0000010001",
  "EventReceivedTime": "2022-09-20T19:28:51.560303-07:00",
  "SourceModuleName": "dns_analytical",
  "SourceModuleType": "im_msvistalog"
}
Disclaimer

While we endeavor to keep the information in this topic up to date and correct, NXLog makes no representations or warranties of any kind, express or implied about the completeness, accuracy, reliability, suitability, or availability of the content represented here.

The accurateness of the content was tested and proved to be working in our lab environment at the time of the last revision with the following software versions:

NXLog 5.5.7535

Last revision: 23 September 2022

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