RDP over Reverse SSH Tunnel WFP

Severity: high
Author: Samir Bousseaden
Source: upstream

Detects svchost hosting RDP termsvcs communicating with the loopback address

MITRE ATT&CK coverage

Tactic	Techniques
Lateral Movement	`T1021.001` Remote Services: Remote Desktop Protocol
Command & Control	`T1090.001` Proxy: Internal Proxy, `T1090.002` Proxy: External Proxy

Event coverage

Provider	Event ID	Title
Security-Auditing	5156	The Windows Filtering Platform has permitted a connection.

Stages and Predicates

Stage 1: `selection`

Stage 2: `sourceRDP`

or:
DestAddress: '::1'
DestAddress|startswith: 127.
SourcePort: 3389

Stage 3: `destinationRDP`

or:
SourceAddress: '::1'
SourceAddress|startswith: 127.
DestPort: 3389

Stage 4: `not 1 of filter*`

or:
Application|endswith: '\thor.exe'
Application|endswith: '\thor64.exe'
FilterOrigin: 'AppContainer Loopback'

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
`Application`	ends_with	`\thor.exe` corpus 7 (sigma 7) `\thor64.exe` corpus 6 (sigma 6)
`DestAddress`	wildcard	`127.*` `::1`
`DestPort`	eq	`3389` corpus 3 (sigma 2, splunk 1)
`FilterOrigin`	eq	`AppContainer Loopback`
`SourceAddress`	wildcard	`127.*` `::1`
`SourcePort`	eq	`3389` corpus 3 (sigma 3)

Neighbors

Stricter alternatives (narrower than this rule)

The rules below may be useful if you find the current rule is too noisy / lacks specificity.

Remote PowerShell Sessions Network Connections (WinRM) [sigma] (adds 2 filters) (first-stage match only; downstream stages may differ)
Uncommon Outbound Kerberos Connection - Security [sigma] (adds 1 filter) (first-stage match only; downstream stages may differ)