Detection rules › Splunk
Proxy Execution via Appcert (Sysmon)
Threat actors may exploit legitimate developer utilities to execute malicious payloads by proxy. One such utility is appcert.exe, a command-line tool included in the Windows Application Certification Kit, which is typically used to verify the compliance of Windows applications with Microsoft's certification standards. This use case detects appcert executions with commands to proxy execution of another binary
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Execution | |
| Stealth |
References
Telemetry coverage
| Provider | Record / event type |
|---|---|
| Sysmon | Event ID 1: Process creation |
Rule body
id: '32821.58285'
title: Proxy Execution via Appcert
description: Threat actors may exploit legitimate developer utilities to execute malicious
payloads by proxy. One such utility is appcert.exe, a command-line tool included
in the Windows Application Certification Kit, which is typically used to verify
the compliance of Windows applications with Microsoft's certification standards.
This use case detects appcert executions with commands to proxy execution of another
binary. Living Off the Land Binary and Scripts (LOLBAS) (LOLBIN)
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
(TERM(appcert) OR "appcert.exe") TERM(test) | regex process!="(?i)\-setupcommandline"|
regex process="(?i)\stest\s"| rex field=process "(?i)-setuppath\s+(?:\"|'')?(?<proxy_exec>[^\s\"'']+\.exe)(?:\"|'')?"
| table _time, host, user, process, parent_*, process_*, proxy_exec | bin span=1s
| stats values(*) as * by _time, host '
techniques:
- defense-evasion:trusted developer utilities proxy execution
technique_id:
- T1127
data_category:
- Windows Sysmon
- Process command-line parameters
references:
- https://attack.mitre.org/techniques/T1127/
- https://attack.mitre.org/techniques/T1218/007/
- https://lolbas-project.github.io/lolbas/OtherMSBinaries/Appcert/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<") (TERM(appcert) OR "appcert.exe") TERM(test)
Stage 2: regex
| regex process!="(?i)\-setupcommandline"
Stage 3: regex
| regex process="(?i)\stest\s"
Stage 4: rex
| rex field=process "(?i)-setuppath\s+(?:\"|')?(?<proxy_exec>[^\s\"']+\.exe)(?:\"|')?"
Stage 5: table
| table _time, host, user, process, parent_*, process_*, proxy_exec
Stage 6: bucket
| bin span=1s
Stage 7: stats
| stats values(*) as * by _time, host
Exclusions
The rule actively suppresses these predicates.
| Field | Kind | Excluded values | Search |
|---|---|---|---|
process | regex_match | "(?i)\-setupcommandline" | excludes:process |
Indicators
These rows show field, operator, and value matches.
| Field | Kind | Values | Search |
|---|---|---|---|
EventCode | eq |
| field:"EventID" kind:eq value:"1" |
process | regex_match |
| field:"CommandLine" kind:regex_match |
Search terms
These SPL tokens match against raw event text.
| Stage | Term |
|---|---|
| 1 | "<EventID>1<" |
| 1 | appcert |
| 1 | "appcert.exe" |
| 1 | test |