Avast Foils Another CCleaner Attack

‘Abiss’ attackers used an older VPN profile to get into Avast’s network and targeted its CCleaner utility.

Two years after cyber-espionage actors infected the CCleaner utility with malware designed to infiltrated certain companies, Avast’s security team has foiled a second attack targeting the widely used system-maintenance program.

The company detected signs of the attack on Sept. 23, when suspicious network behavior tipped off its security team. The attackers gained access through compromised VPN credentials that used an old profile not requiring two-factor authentication. The attackers were able to compromise two separate accounts and access the internal network, Avast said in a statement on its site today.

The attack failed to advance beyond the early stages, says Jaya Baloo, Avast’s chief information security officer, who started on Oct. 1 as the investigation kicked off.

“The worst-case scenario was that they could try to do what they did before: Get code-signing keys, be able to push out malware, and send [malicious code] using valid updates,” she says. “So we looked for that, but we didn’t find it. We assumed nothing and looked at all the old versions of stuff we released in the last six months. … We checked and rechecked.”

The incident could have ended much worse, as it did two years ago. In July 2017, attackers managed to infiltrate the network of Piriform, maker of CCleaner, following Avast’s acquisition of the company, and pushed out malware-infected updates to 2.27 million users. The company was not a target of opportunity. The attackers pushed secondary infections to just 20 victims machines, targeting companies including Microsoft, Google, Sony, Cisco, and Akamai.

“From the insights we have gathered so far, it is clear that this was an extremely sophisticated attempt against us that had the intention to leave no traces of the intruder or their purpose, and that the actor was progressing with exceptional caution in order to not be detected,” Avast stated in the most recent blog post. “We do not know if this was the same actor as before and it is likely we will never know for sure, so we have named this attempt ‘Abiss’.”

After initially detecting the suspicious access on Sept. 23, the company found a second user account had also been used by the attackers. Tracking back the history of suspicious activity, the company found the first attempts by the attacker to infiltrate the system dated back to May 14.

The company then tracked the known compromised user accounts. While the original user account did not have administrative access, the attackers used a privilege-escalation exploit to gain greater permissions on the network, Avast stated. The attacker was able to replicate the Active Directory, a step toward attempting to retrieve additional credentials, but did not advance further, the company said.

The attack required that Baloo jump in with both feet into her new role. While she was hired earlier in the summer, she still had not left her previous job and was traveling when she got the call.

“The first order of business was to …. figure out where the bathroom is and examine all those logs,” she says.

As part of its response, Avast collaborated with the Czech intelligence agency, known as the Security Information Service (BIS), the cybersecurity section of the local Czech police, and a third-party incident response and forensics team.

Avast has a very technical team, who had learned a great deal from the attack two years ago, Baloo says. Yet there are still lessons to be learned from this time around.

The first is to better analyze the data the company is collecting. The initial alert had been detected by the company, but was deemed a false positive — not a threat. While many companies can cut out noisy data sources, Avast needs to analyze as much data possible because that is the company’s business, she says.

“This is really challenging, especially in a company whose business it is to look for the bad guys,” she says. “You have a lot of data, and so you have two different extremes — having a lot of data but not using it or being crippled by the immense amount of data you are getting.

The company also needs to better segment its permissions, which is difficult because everyone in the company is quite technical and wants to do as much on his or her own as possible, she says.

“The people are capable and have hands-on credibility, so they have a lot of leeway to ask for a lot of privileges on the network because they can handle it,” Baloo says. “But nothing is better for security than segmentation, isolation, and asking people to jump through a few more hoops before giving them access to the crown jewels.”

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