topic Regex for looking at executables in a specific folder in Splunk Search

Regex for looking at executables in a specific folder

tbradsher86 — Tue, 13 Aug 2019 16:39:16 GMT

Hi All,

I am trying to create a search that will parse our endpoint logs for any executable that have been run from the Desktop or Downloads folders and any sub folders. Most searches I try return a large number of false positives (product names or folders have desktop or downloads in the name, but they aren't specifically in that folder. So to combat this I'm trying to rex the specific folder. Using the regex I have below on regex101 it works exactly how I expect. However in splunk I get, first a missing parenthesis error, and if I arbitrarily add another close parenthesis I get "look back is not a fixed length" error. Thoughts?

sourcetype=endpointsource AND event_name=process_ran
| rex field=CommandLine "(?<=\\Desktop|Downloads\\)(?<EXE_RAN>.*\.exe)"
| table _time ComputerName TargetFileName EXE_RAN user

Example of it working on regex101: https://regex101.com/r/24uxEB/1

Thanks!

Re: Regex for looking at executables in a specific folder

jpolvino — Tue, 13 Aug 2019 16:47:34 GMT

Here is one way:

| rex field=CommandLine ".*(Desktop|Downloads)\\\(?<EXE_RAN>.*\.exe)"

https://regex101.com/r/24uxEB/2

Re: Regex for looking at executables in a specific folder

mayurr98 — Tue, 13 Aug 2019 16:51:13 GMT

Try this:

| rex field=CommandLine "(?<=\\\Desktop|Downloads\\\)(?<EXE_RAN>.*\.exe)"

Also try run anywhere search

| makeresults 
| eval data="C:\users\user1\Downloads\blah.exe,C:\Users\user234\Downloads\sqldeveloper-17.4.0.355.2349-x64\sqldeveloper\sqldeveloper\bin\sqldeveloper64W.exe,C:\Users\user9823\AppData\Local\iManage\Installer\Updates\iManage Work Desktop for Windows x86.exe,C:\Users\johnsmith\Desktop\dataloader-44.0.0.exe" 
| makemv data delim="," 
| mvexpand data 
| table data 
| rex field=data "(?<=\\\Desktop|Downloads\\\)(?<EXE_RAN>.*\.exe)"

Re: Regex for looking at executables in a specific folder

tbradsher86 — Tue, 13 Aug 2019 16:51:41 GMT

This gets me the following error still:

Error in 'rex' command: Encountered the following error while compiling the regex '.(Desktop|Downloads)(?..exe)': Regex: unmatched closing parenthesis.

Re: Regex for looking at executables in a specific folder

jpolvino — Tue, 13 Aug 2019 16:55:30 GMT

Sorry, forgot Splunk needed another escape character. Fixed above!

Re: Regex for looking at executables in a specific folder

tbradsher86 — Wed, 14 Aug 2019 11:47:32 GMT

This worked perfectly, that extra escape character really got me. Thank you!