Abnormally Large DNS Response
editAbnormally Large DNS Response
editSpecially crafted DNS requests can manipulate a known overflow vulnerability in some Windows DNS servers which result in Remote Code Execution (RCE) or a Denial of Service (DoS) from crashing the service.
Rule type: query
Rule indices:
- packetbeat-*
- filebeat-*
Severity: medium
Risk score: 47
Runs every: 5 minutes
Searches indices from: now-6m (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
References:
- https://research.checkpoint.com/2020/resolving-your-way-into-domain-admin-exploiting-a-17-year-old-bug-in-windows-dns-servers/
- https://msrc-blog.microsoft.com/2020/07/14/july-2020-security-update-cve-2020-1350-vulnerability-in-windows-domain-name-system-dns-server/
- https://github.com/maxpl0it/CVE-2020-1350-DoS
Tags:
- Elastic
- Network
- Threat Detection
- Lateral Movement
Version: 1
Added (Elastic Stack release): 7.10.0
Rule authors: Elastic
Rule license: Elastic License
Potential false positives
editEnvironments that leverage DNS responses over 60k bytes will result in false positives - if this traffic is predictable and expected, it should be filtered out. Additionally, this detection rule could be triggered by an authorized vulnerability scan or compromise assessment.
Investigation guide
editDetection alerts from this rule indicate an attempt was made to exploit CVE-2020-1350 (SigRed) through the use of large DNS responses on a Windows DNS server. Here are some possible avenues of investigation:
- Investigate any corresponding Intrusion Detection Signatures (IDS) alerts that can validate this detection alert.
-
Examine the
dns.question_typenetwork fieldset with a protocol analyzer, such as Zeek, Packetbeat, or Suricata, forSIGorRRSIGdata. - Validate the patch level and OS of the targeted DNS server to validate the observed activity was not large-scale Internet vulnerability scanning.
- Validate that the source of the network activity was not from an authorized vulnerability scan or compromise assessment.
Rule query
editevent.category:(network or network_traffic) and destination.port:53 and (event.dataset:zeek.dns or type:dns or event.type:connection) and network.bytes > 60000
Threat mapping
editFramework: MITRE ATT&CKTM
-
Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
-
Technique:
- Name: Exploitation of Remote Services
- ID: T1210
- Reference URL: https://attack.mitre.org/techniques/T1210/