Pierluigi Paganini March 27, 2018

Researchers at Morphisec have uncovered a watering hole attack on leading Hong Kong Telecom website exploiting the CVE-2018-4878 flash vulnerability.

Security experts at Morphisec have discovered a watering hole attack on leading Hong Kong Telecom website exploiting the CVE-2018-4878 flash vulnerability.

In a watering hole attack, hackers infect the websites likely to be visited by their targeted victims, this technique requires more effort than common spear-phishing attack and it is usually associated with APT groups.

Early February, Adobe rolled out an emergency patch that fixed two critical remote execution vulnerabilities, including the CVE-2018-4878, after North Korea’s APT group was spotted exploiting it in targeted attacks.

At the time, South Korea’s Internet & Security Agency (KISA) warned of a Flash zero-day vulnerability (CVE-2018-4878) that has reportedly been exploited in attacks by North Korea’s hackers.

By the end of February, the researchers at Morphisec reported that threat actors were exploiting the use-after-free flaw to deliver malware.

“On March 21,2018, Morphisec Labs began investigating the compromised website of a leading Hong Kong Telecommunications company after being alerted to it by malware hunter @PhysicalDrive0.” reads the analysis published by Morphisec.

“The investigation, conducted by Morphisec researchers Michael Gorelik and Assaf Kachlon, determined that the Telecom group’s corporate site had indeed been hacked. Attackers added an embedded Adobe Flash file that exploits the Flash vulnerability CVE-2018-4878 on the main home.php page. The attack is a textbook case of a watering hole attack.”

Threat actors behind the attack uncovered by the experts adopted advanced evasive techniques, they used a purely fileless malicious code, without persistence or any trace on the disk. It is interesting to note also the usage of a custom protocol over the 443 port.

The Flash exploit used in this attack was similar to the one involved in the attacks involving the CVE-2018-4878 vulnerability, but it employs a different shellcode executed post exploitation.

“Generally, this advanced type of watering hole attack is highly targeted in nature and suggests that a very advanced group is behind it,” continues the post.

“The Flash exploit that was delivered has a high degree of similarity to the previously published analysis of the CVE-2018-4878. The major difference in this exploit is in the shellcode that is executed post exploitation”

The shellcode executes rundll32.exe and overwrites the content of the memory with a malicious code that was designed to download additional code directly into the memory of the rundll32 process.

The additional code downloaded directly into the memory of the rundll32 process includes Metasploit Meterpreter and Mimikatz modules.

The analysis of the modules revealed that were compiled on February 15, a few days before the attack.

“As our analysis shows, this watering hole attack is of advanced evasive nature. Being purely fileless, without persistence or any trace on the disk, and the use of custom protocol on a non-filtered port, makes it a perfect stepping stone for a highly targeted attack chain. This clearly suggests that very advanced threat actors are responsible for it,” Morphisec says.

The experts noticed that despite the advanced evasive features, the attack used basic Metasploit framework components that were compiled just before the attack and did not show any sophistication, obfuscation or evasion.

At this time, the company hasn’t attributed the attack to a specific threat actor, it is still investigating the incident.

Pierluigi Paganini

(Security Affairs – CVE-2018-4878, watering hole)

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