Abnormally Large DNS Responseedit
Specially 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: 4 (version history)
Added (Elastic Stack release): 7.10.0
Last modified (Elastic Stack release): 7.13.0
Rule authors: Elastic
Rule license: Elastic License v2
Potential false positivesedit
Environments 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 guideedit
## Triage and analysis ### Investigating Large DNS Responses Detection 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_type` network fieldset with a protocol analyzer, such as Zeek, Packetbeat, or Suricata, for `SIG` or `RRSIG` data. - 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 queryedit
event.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 mappingedit
Framework: 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/
Rule version historyedit
- Version 4 (7.13.0 release)
-
- Formatting only
- Version 3 (7.12.0 release)
-
- Formatting only
- Version 2 (7.11.2 release)
-
- Formatting only