Detection rules › Splunk
ProtocolHandler.exe File Download (Sysmon)
ProtocolHandler.exe is a component of Microsoft Office and is typically used for accessing Microsoft Office documents from Outlook and Sharepoint. Adversaries can use ProtocolHandler.exe to download files. This use case detects executions of ProtocolHandler.exe followed by URLs in the command line. Allowlisting of expected Sharepoint domains is recommended to reduce false positives. LOLBINS/LOLBAS
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Command & Control | T1105 Ingress Tool Transfer |
References
Event coverage
| Provider | Event | Title |
|---|---|---|
| Sysmon | Event ID 1 | Process creation |
Rule body yaml
id: '21901.38720'
title: ProtocolHandler.exe File Download
description: ProtocolHandler.exe is a component of Microsoft Office and is typically
used for accessing Microsoft Office documents from Outlook and Sharepoint. Adversaries
can use ProtocolHandler.exe to download files. This use case detects executions
of ProtocolHandler.exe followed by URLs in the command line. Allowlisting of expected
Sharepoint domains is recommended to reduce false positives. LOLBINS/LOLBAS
logic_format: Splunk
logic: '`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<")
"ProtocolHandler.exe" | regex process="(?i)ProtocolHandler\.exe\"?\s+\"?[A-Za-z0-9]{2,6}:\/\/"
| table _time, host, user, signature_id, process, process_*, parent_process_path,
parent_process_name | bin span=1s | stats values(*) as * by _time, host '
techniques:
- command-and-control:ingress tool transfer
technique_id:
- T1105
data_category:
- Windows Sysmon
- Process command-line parameters
references:
- https://pentera.io/blog/the-lol-isnt-so-funny-when-it-bites-you-in-the-bas/
- https://lolbas-project.github.io/lolbas/OtherMSBinaries/ProtocolHandler/
Stages and Predicates
Stage 1: search
`get_endpoint_data` `get_endpoint_data_sysmon` (TERM(EventCode=1) OR "<EventID>1<") "ProtocolHandler.exe"
Stage 2: regex
| regex process="(?i)ProtocolHandler\.exe\"?\s+\"?[A-Za-z0-9]{2,6}:\/\/"
Stage 3: table
| table _time, host, user, signature_id, process, process_*, parent_process_path, parent_process_name
Stage 4: bucket
| bin span=1s
Stage 5: stats
| stats values(*) as * by _time, host
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.
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>1<" |
| 1 | "ProtocolHandler.exe" |