Security researchers have discovered that the new SLUB backdoor is receiving attack commands from GitHub and relying on Slack for communicating with its attackers.

Trend Micro detailed how this malware campaign began with watering hole attacks that redirected users to webpages hosting malicious code. The campaign proceeded with infection whenever these attacks caught someone with a machine that was not secured from CVE-2018-8174, a VBScript engine vulnerability patched by Microsoft back in May 2018.

Upon exploitation, the attack downloaded a dynamic-link library (DLL) and ran a PowerShell command. This process loaded a downloader that, in turn, downloaded and ran a second executable file containing the SLUB backdoor.

Detected as Backdoor.Win32.SLUB.A, the SLUB backdoor is a threat written in C++ that stands out for two reasons:

• First, it embeds two authorization tokens to communicate with Slack’s application programming interface (API).
• Second, it downloads a gist snippet from GitHub and parses it to search for commands.

The backdoor uses these two steps to post the result of its commands in a private Slack channel within a workspace using the embedded tokens. With this flow in place, digital attackers can use SLUB to take screen captures, create archive files and exfiltrate information.

The Ongoing Relevance of Watering Hole Attacks

This campaign isn’t the only recent operation to use watering hole attacks. For example, ESET detected one such campaign in November 2018, in which the OceanLotus group used watering hole attacks to target several websites in Southeast Asia. Several months later, ESET reported that the APT LuckyMouse group had preyed on the International Civil Aviation Organization using a watering hole attack.

These incidents illustrate how watering hole attacks pose an ongoing threat to organizations. Indeed, Carbon Black found that more than one-fifth (21 percent) of financial services companies had recently experienced this type of attack. Threat actors could use a successful attack in those cases to steal money and undermine customer trust in the financial institutions.

How to Defend Against Threats Like the SLUB Backdoor

Security professionals can defend against digital threats like the SLUB backdoor by using a layered security approach. This strategy should include machine learning and threat detection sandboxing to strengthen endpoint defenses against emerging threats, such as fileless malware.

Organizations should also practice risk-based vulnerability management to prioritize the software security flaws they should patch first.