Unusual File Deletion by Dns.exe

Severity: high
Author: Tim Rauch (Nextron Systems), Elastic (idea)
Source: upstream

Detects an unexpected file being deleted by dns.exe which my indicate activity related to remote code execution or other forms of exploitation as seen in CVE-2020-1350 (SigRed)

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1133` External Remote Services
Persistence	`T1133` External Remote Services

Event coverage

Provider	Event ID	Title
Sysmon	23	FileDelete (File Delete archived)
Sysmon	26	FileDeleteDetected (File Delete logged)

Stages and Predicates

Stage 1: `selection`

Image|endswith: '\dns.exe'

Stage 2: `not filter`

TargetFilename|endswith: '\dns.log'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`Image`	ends_with	`\dns.exe` corpus 2 (sigma 2)
`TargetFilename`	ends_with	`\dns.log` corpus 2 (sigma 2)