topic PoshC2 false positive in Advanced Threat Prevention Discussions

PoshC2 false positive

MichaelWrigh — Fri, 11 Mar 2022 10:17:48 GMT

Hello,

We are seeing what appears to be false positive detections for the PoshC2C vulnerability signatures that was released recently. Connections going to Google and BBC, is anyone else seeing the same thing here?

Re: PoshC2 false positive

lvultao — Fri, 11 Mar 2022 15:07:42 GMT

I think I'm seeing this too. I have a particular user where I'm seeing this when they click the google logo to go back to the main search page. I'm getting Threat ID: 86523

Re: PoshC2 false positive

Adrian_Jensen — Fri, 11 Mar 2022 15:37:55 GMT

Confirmed. I just tried the same and got the alert for PoshC2 (ThreatID: 86523, release 8540 2022-03-10). Extremely easy to replicate:

1) Do a Google search

2) Click the Google logo on the search results page

3) Page redirects to hxxps://google.com/webhp?hl=en&sa=X&ved=<trackingID> and is blocked as a threat

Re: PoshC2 false positive

SecurityEngineering — Fri, 11 Mar 2022 18:56:51 GMT

It appears that the rule looks for the URL strings listed on github[.]com/johnjohnsp1/PoshC2_Python/blob/master/Config.py:

URLS = '"adsense/troubleshooter/1631343/","adServingData/PROD/TMClient/6/8736/","advanced_search?hl=en-GB&fg=","async/newtab?ei=","babel-polyfill/6.3.14/polyfill.min.js=","bh/sync/aol?rurl=/ups/55972/sync?origin=","bootstrap/3.1.1/bootstrap.min.js?p=","branch-locator/search.asp?WT.ac&api=","business/home.asp&ved=","business/retail-business/insurance.asp?WT.mc_id=","cdb?ptv=48&profileId=125&av=1&cb=","cis/marketq?bartype=AREA&showheader=FALSE&showvaluemarkers=","classroom/sharewidget/widget_stable.html?usegapi=","client_204?&atyp=i&biw=1920&bih=921&ei=","load/pages/index.php?t=","putil/2018/0/11/po.html?ved=","q/2018/load.php?lang=en&modules=","status/995598521343541248/query=","TOS?loc=GB&hl=en&privacy=","trader-update/history&pd=","types/translation/v1/articles/","uasclient/0.1.34/modules/","usersync/tradedesk/","utag/lbg/main/prod/utag.15.js?utv=","vs/1/vsopts.js?","vs/site/bgroup/visitor/","w/load.php?debug=false&lang=en&modules=","web/20110920084728/","webhp?hl=en&sa=X&ved=","work/embedded/search?oid="'

Re: PoshC2 false positive

Adrian_Jensen — Fri, 11 Mar 2022 19:50:54 GMT

@SecurityEngineering wrote:
"webhp?hl=en&sa=X&ved="

Bingo.... that is the path of the Google redirect back to the main search page.

@MichaelWrigh Have you opened a false alert report with PA?

Re: PoshC2 false positive

MichaelWrigh — Mon, 14 Mar 2022 16:52:56 GMT

Not yet, am hoping to get it done soon though. Am on a training course this week but should be bale to find the time.

Re: PoshC2 false positive

Adrian_Jensen — Mon, 14 Mar 2022 17:01:27 GMT

It looks like someone has already submitted a false positive report. The 8541 release has a single note about improving PoshC2 detection. Testing against Google I am no longer seeing the false alert.