A new AdLoad Trojan Element is slipping through Apple’s YARA signature-based XProtect built-in antivirus tech the insert Macs as part of multiple operations tracked by American cybersecurity firm SentinelOne. AdLoad is a widespread malware targeting the macOS platform since at least late 2017 and utilized to set up various malicious payloads, including adware and Potentially Unwanted Applications (PUAs). This Trojan can also harvest system data that later get transmit to remote servers controlled by its operators.

How has this Trojan Actively Increasing since July?

This massive scale and ongoing attacks have started as early as November 2020, according to SentinelOne threat researcher Phil Stokes, with an increase in activity beginning with July and the beginning of August. Once it infects a Mac, AdLoad will install a Man-in-The-Middle (MiTM) web proxy to hijack search engine results and inject advertisements into web pages for monetary gain.

It will also gain persistence on infected Macs by installing LaunchAgents and LaunchDaemons and, in some cases, user cronjobs that run every two and a half hours. While observing this operation, the researcher inspected more than 220 samples, 150 of them different and undetected by Apple’s built-in antivirus even though XProtect now appears with approximately a dozen AdLoad signatures.

Various of the samples identified by SentinelOne are also signed with valid Apple-issued Developer ID certificates, while others are also approved to operate under default Gatekeeper settings. 

“At the time of writing, XProtect was last updated about June 15th. None of the samples we detected are known to XProtect since they do not match any of the scanner’s current set of Adload rules,” Stokes ended. “The truth that hundreds of different samples of a well-known adware alternative have been flowing for at least 10 months and yet still remain undetected by Apple’s built-in malware scanner confirms the requirement of adding additional endpoint security controls to Mac devices.” 

Why it is Challenging to Evade Threats?

To put things into perspective, Shlayer, another common macOS malware strain that has also been able to bypass XProtect before and infect Macs with other malicious payloads, has hit over 10% of all Apple computers monitored by our experts.

Its producers also got their Trojan through Apple’s automated notarizing process and combined the capacity to disable the Gatekeeper protection mechanism to execute unsigned second-stage payloads. Recently, Shlayer also utilized a macOS zero-day to bypass Apple’s File Quarantine, Gatekeeper, and Notarization security checks and download second-stage malicious payloads on compromised Macs.

While both the AdLoad and Shlayer now only set up adware and bundleware as secondary payloads, their creators can quickly switch to more dangerous malware, including ransomware or wipers, at any time. Today, we have a level of malware on the Mac that we don’t find satisfactory and that is much worse than iOS,” said Craig Federighi, Apple’s head of software, under oath while analyzing in the Epic Games vs. Apple trial in May.