Threat Level: green Handler on Duty: Didier Stevens

SANS ISC: New Waves of Scans Detected by an Old Rule SANS ISC InfoSec Forums

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New Waves of Scans Detected by an Old Rule

Who remembers the famous ShellShock (CVE-2014-6271)? This bug affected the bash shell in 2014 and was critical due to the facts that it was easy to exploit and that bash is a widespread shell used in many tools/applications. So, at this time, I created an OSSEC alerts to report ShellShock exploitation attempts against my servers. Still today, I'm getting a hit on this rule from time to time.

But, for 15 days, I started to get more alerts like this one:

Received From: (xxxx) x.x.x.x->/www/log/xxxxxxx.access
Rule: 100705 fired (level 10) -> "Shellshock Attempt"
Src IP: x.x.x.x
Portion of the log(s):

x.x.x.x - - [04/Apr/2019:07:31:19 +0200] "GET /type.php?template=tag_(){};@unlink(_FILE_);assert($_POST[T00ls]);{//../rss HTTP/1.1" 301 604 "http://xxxxxxx" "Mozilla/5.0 (compatible; Baiduspider/2.0; +\xa3\xa9"

This rule fired 34 times since mid-March and I'm still getting, at least, one per day. This query is related to CVE-2018-19127 which affects phpcms[1]. By exploiting the vulnerability, the attackers get a webshell on the server (details are available on a Github page[2]). Some details about the hits I found:

Three different User-Agents have been used:

Mozilla/4.0 (compatible; MSIE 9.0; Windows NT 6.1)                                            24
Mozilla/5.0 (compatible; Baiduspider/2.0; +\xa3\xa9    2
python-requests/2.21.0                                                                        8

Scan sources are clearly identifiable: 

The scan in itself is not critical (except if you're still running a vulnerable version of phpcms of course) but what's interesting here? An alert created in your SIEM or log management solution a long time ago can still be relevant!


Xavier Mertens (@xme)
Senior ISC Handler - Freelance Cyber Security Consultant

I will be teaching next: Reverse-Engineering Malware: Malware Analysis Tools and Techniques - SANS Paris March 2021


579 Posts
ISC Handler
Apr 4th 2019

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