New SynkLoader backdoor malware targets Microsoft Teams users via fake IT helpdesk

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Expel researchers warn of SynkLoader backdoor spread via fake IT help desk Teams messages

Malware modules include PhishLocker (fake login screen harvesting OS passwords) and Interactive Shell for remote control

Defenses: distrust unsolicited Teams DMs, verify with IT before installing apps, and train staff against social engineering

For roughly a month now, cybercriminals have been targeting organizations with a new backdoor malware called SynkLoader.

According to security researchers Expel, the attack starts with social engineering. Victims would get a Microsoft Teams message from a person claiming to be from the company’s IT help desk. They would tell the victim their computer is having an issue, and that they need to install a “PowerShell Cleaner”. This fake program is nothing more than a malicious framework, hosted on Microsoft Azure to increase its trustworthiness.

The malware itself comes with a number of different modules, giving the attacker a range of features, from harvesting system information, to creating a reverse proxy. Two particularly worrying modules are called PhishLocker and Interactive Shell. The former creates a convincing, yet fake, Windows lock screen, which can harvest the user’s OS login password.

This is not SickKids' first attack

BleepingComputer argues that with this password the attackers could “access corporate environments from the infected device, bypassing IP allow-list restrictions”. Those with a sharper eye might spot the ruse, as a simple Alt + Tab shows that the login screen is nothing more than a “full-screen borderless GUI application”.

The other module - Interactive Shell, allows threat actors to remotely execute PowerShell commands and receive the output, which essentially grants them full control over the infected device.

The full list of Indicators of Compromise (IoC) can be found on this link . To defend against these types of attacks, target companies should instruct their employees not to trust unsolicited Teams messages at face value, and not to install any applications without double-checking (calling) with their IT department first.

Alongside phone calls, Microsoft Teams is one of the most-used channels for initial contact and compromise. Also, employees remain the weakest link in every company’s cybersecurity chain, unwillingly granting attackers access or sharing login credentials.

Via BleepingComputer