Detection rules › Splunk
wuauclt.exe Network Connection (Sysmon)
wuauclt.exe is the Windows Update client. It can be abused to proxy execution of malicious code as documented in the LOLBAS project. This use case detects network connection events with wuauclt.exe. Connections to Microsoft-owned IPs are expected behavior and have been filtered out
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Stealth | T1218 System Binary Proxy Execution |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 3 | Network connection |
Rule body yaml
id: '25039.46452'
title: wuauclt.exe Network Connection
description: wuauclt.exe is the Windows Update client. It can be abused to proxy execution
of malicious code as documented in the LOLBAS project. This use case detects network
connection events with wuauclt.exe. Connections to Microsoft-owned IPs are expected
behavior and have been filtered out. Living Off the Land Binary and Scripts (LOLBAS)
(LOLBIN)
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=3) OR "<EventID>3<")
"wuauclt" | where not match(dest_ip, "^(20\.18[4-9]\.|20\.19[0-1]\.|23\.79\.|51\.10[3-5]\.|52\.239\.)")
and match(process_name, "(?i)wuauclt\.exe") | table _time, host, user, signature_id,
process, process_name, parent_process_path, parent_process_name, src_ip, dest_ip
`group_events("host,1)` '
techniques:
- defense-evasion:system binary proxy execution
technique_id:
- T1218
data_category:
- Windows Sysmon
references:
- https://lolbas-project.github.io/lolbas/Binaries/Wuauclt/
Stages and Predicates
Stage 1: search
search EventCode=3 source="*" source IN ("WinEventLog:Microsoft-Windows-Sysmon/Operational", "XmlWinEventLog:Microsoft-Windows-Sysmon/Operational")
Stage 2: where
where NOT dest_ip="*^(20\\.18[4-9]\\.|20\\.19[0-1]\\.|23\\.79\\.|51\\.10[3-5]\\.|52\\.239\\.)*" process_name="*(?i)wuauclt\\.exe*"
Stage 3: table
table _time, dest_ip, host, parent_process_name, parent_process_path, process, process_name, signature_id, src_ip, user
Stage 4: bucket
bucket _time
Stage 5: stats
stats BY host, _time
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
dest_ip | match | "^(20\.18[4-9]\.|20\.19[0-1]\.|23\.79\.|51\.10[3-5]\.|52\.239\.)" |
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 |
|---|---|---|
EventCode | eq |
|
process_name | match |
|
Search terms
Bare-string tokens in the SPL search body. Splunk matches each token against _raw (the untyped raw event text) anywhere it appears, not against a specific field. These don't surface in the Indicators table because they aren't predicates on a known field.
| Stage | Term |
|---|---|
| 1 | TERM |
| 1 | "<EventID>3<" |
| 1 | "wuauclt" |