Attackers Focus on More Disruptive Ransomware Infections

In April 2018, a cybercriminal operation started infecting systems using compromised websites as a launching pad to convince employees at corporations to download what appeared to be a browser update.

A year later, the cybercriminals are at it again. Between May and September, security services firm FireEye has worked with at least seven companies broadly infected by a new ransomware campaign following a similar malicious browser update — a campaign FireEye is calling FakeUpdates. In the intervening year, the campaign has evolved to include new post-exploitation toolkits and techniques, including wider reconnaissance, credential harvesting, lateral movement, and privilege escalation.

In a blog post, FireEye described one of the attacks from beginning to end, with the hope the information can help companies blunt the trend of more extensive infections, says Kimberly Goody, a manager of intelligence analysis at FireEye.

"In a lot of these cases — where we see the post-compromise distribution of ransomware, and instead of infecting a handful of machines, [the attackers] are infecting hundreds of machines across the victim's network — they are ultimately causing a significant amount of disruption to [the victim's] daily workflow or business," she says. "As a result of that, the victims were forced to pay. We were able to see that from beginning to end, these are the full details of the attack chain."

The attack demonstrates that attackers are continuing to refine their strategies and attempting to adjust to victims' resolve to not pay ransoms. In July, for example, a group of mayors representing the largest 1,400 towns in the United States pledged not to pay ransoms to cyberattackers. The next month, almost two dozen Texas municipal agencies and public organizations suffered massive ransomware infections that hobbled operations. 

Attackers are far more flexible in their approaches to attacking organizations. They are no longer just searching for sensitive — and sellable — information, but willing to infect systems if they believe they can get the victim to pay, argued six FireEye researchers in the analysis.

"Ransomware proves that threat actors don't need to get access to the most sensitive parts of your organization – they need to get access to the ones that will disrupt business processes," the researchers said. "This widens your attack surface, but luckily, also gives you more opportunity for detection and response."

Initial compromises are often achieved through phishing attacks or malvertising. The FakeUpdates campaign that kicks off will often appear as an advertisement that claims "You are using an older version of Chrome" or another browser.

Vulnerable websites are key to the attackers' capability to spread their malware, FireEye said. A "large number of compromised sites" are used to host and serve the fake browser update after being exploited through vulnerable and outdated content management systems, the firm said.

Once downloaded and executed, the FakeUpdates program uses the Windows Scripting Host to fingerprint the infected system, creates a backdoor, takes screenshots of the desktop, and sends them to attacker. The program then contacts a command-and-control server through custom HTTP calls and passes information on the system, user, security software, and running processes.

The command-and-control server then sends one of several different payloads, including the Dridex or Chthonic banking Trojan, the AZORult spyware program, or the remote access tool NetSupport.

The attack does not necessarily use "sophisticated" malware," Goody says.

"They are not really developing custom malware, so 'sophisticated' isn't the right word," she says. "In a way, it is more sophisticated because you are using less obvious tools if it is something that the organization uses internally to manage their IT network."

In several cases, the attacks expanded to infect other systems and install ransomware — either Bitpaymer or, in one case, Doppelpaymer — on the systems.

The infection underscores the evolution of many ransomware groups, from opportunistic attackers to more sophisticated operators, that infect many systems to cause more pain to targeted enterprises, FireEye said.

"[T]hreat actors are now coupling ransomware with multiple toolkits or other malware families to gain stronger footholds into an environment," the security researchers stated in the blog post. "[W]e witnessed a threat actor move through multiple toolsets — some automated, some manual — with the ultimate goal of holding the victim organization hostage."

Companies need to harden their networks against the spread of ransomware by attackers who may have established a beachhead inside the network. Segmenting each endpoint with specific firewall rules and locking down Remote Desktop Protocol (RDP) interactions can slow the spread of malware. In addition, hidden hard drive and administrative shares should be disabled to prevent their use in an infection. Finally, user and administrative credentials need to be encrypted and the availability of privileged accounts limited, the firm stated in its guidance.

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