CCleaner Compromised to Distribute Malware for Almost a Month
By Catalin Cimpanu
BleepingComputer.com

September 18, 2017   05:11 AM

https://www.bleepingcomputer.com/news/security/ccleaner-compromised-to-distribute-malware-for-almost-a-month/

[image: CCleaner app]

Version 5.33 of the CCleaner app offered for download between August 15 and
September 12 was modified to include the Floxif malware, according to a
report published by Cisco Talos a few minutes ago.

Floxif is a malware downloader that gathers information about infected
systems and sends it back to its C&C server. The malware also had the
ability to download and run other binaries, but at the time of writing,
there is no evidence that Floxif downloaded additional second-stage
payloads on infected hosts.

The malware collected information such as computer name, a list of
installed software, a list of running processes, MAC addresses for the
first three network interfaces, and unique IDs to identify each computer in
part. Researchers noted that the malware only ran on 32-bit systems. The
malware also quit execution if the user was not using an administrator
account.
Threat actor compromised CCleaner infrastructure

Cisco Talos security researchers detected the tainted CCleaner app last
week while performing beta testing of a new exploit detection technology.

Researchers identified a version of CCleaner 5.33 making calls to
suspicious domains. While initially, this looked like another case where a
user downloaded a fake, malicious CCleaner app, they later discovered that
the CCleaner installer was downloaded from the official website and was
signed using a valid digital certificate.

Cisco Talos believes that a threat actor might have compromised Avast's
supply chain and used its digital certificate to replace the legitimate
CCleaner v5.33 app on its website with one that also contained the Floxif
trojan.

It is unclear if this threat actor breached Avast's systems without the
company's knowledge, or the malicious code was added by "an insider with
access to either the development or build environments within the
organization."
Clean CCleaner versions released

Avast bought Piriform
<https://www.bleepingcomputer.com/news/business/avast-buys-piriform-the-company-behind-ccleaner-and-recuva/>
— CCleaner's original developer — in July this year, a month before
CCleaner 5.33 was released.

Piriform acknowledged the incident in a blog post
<http://www.piriform.com/news/blog/2017/9/18/security-notification-for-ccleaner-v5336162-and-ccleaner-cloud-v1073191-for-32-bit-windows-users>
today. The company said they found the malware in CCleaner version
5.33.6162 and CCleaner Cloud version 1.07.3191.

On September 13, Piriform released CCleaner 5.34 and pushed an update
(v1.07.3214) to CCleaner Cloud users that do not contain the malicious code.
Updating to recent versions removes malware

In an email to *Bleeping Computer*, Avast CTO Ondrej Vlcek said that
updating CCleaner to the most recent recent versions fixes any issues, as
"the only malware to remove is the one embedded in the CCleaner binary
itself."

"The affected software (CCleaner v5.33.6162 and CCleaner Cloud v1.07.3191)
has been installed on 2.27M machines from its inception up until now,"
Vlcek also added. "We believe that these users are safe now as our
investigation indicates we were able to disarm the threat before it was
able to do any harm."

"There is no indication or evidence that any additional "malware" has been
delivered through the backdoor," Vlcek added.

Technical details about the Floxif malware's mode of operation, infection
process, and indicators of compromise are available in a Cisco Talos report
here
<http://blog.talosintelligence.com/2017/09/avast-distributes-malware.html>.

[image: Floxif modus operandi]
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