OnionPoison: malicious Tor Browser installer served through a popular Chinese YouTube channel

Pierluigi Paganini October 05, 2022

OnionPoison: researchers reported that an infected Tor Browser installer has been distributed through a popular YouTube channel.

Kaspersky researchers discovered that a trojanized version of a Windows installer for the Tor Browser has been distributed through a popular Chinese-language YouTube channel.

The campaign, named OnionPoison, targeted users located in China, where the Tor Browser website is blocked. Users in China often attempt to download the Tor browser from third-party websites.

In the OnionPoison campaign, threat actors shared a link to a malicious Tor installer posting it on a popular Chinese-language YouTube channel providing info on the anonymity on the internet.

OnionPoison Tor Browser

The channel has more than 180,000 subscribers and according to Kaspersky the video with the malicious link had more than 64,000 views at the time of the discovery. The video was posted on January 2022, and according to Kaspersky’s telemetry, the first victims were compromised in March 2022.

The malicious version of the installer installs a malicious Tor Browser that is configured to expose user data, including the browsing history and data entered into website forms. The experts also discovered that the libraries bundled with the malicious Tor Browser is infected with spyware.

“More importantly, one of the libraries bundled with the malicious Tor Browser is infected with spyware that collects various personal data and sends it to a command and control server. The spyware also provides the functionality to execute shell commands on the victim machine, giving the attacker control over it.” reads Kaspersky’s analysis. “We decided to dub this campaign ‘OnionPoison’, naming it after the onion routing technique that is used in Tor Browser.”

The description of the video includes two links, one to the official Tor Browser website, while the other points to the malicious Tor Browser installer hosted on a Chinese cloud sharing service.

The malicious installer has a file size of 74.1 MB. Upon executing the installer a malicious Tor Browser is installed, it has the same UI of the original Tor Browser. The malicious installer is not digitally signed and the malicious installer also drops some files that are different from the ones bundled with the original installer

“The file freebl3.dll is present in the original Tor Browser installer; however, its contents are entirely different from the DLL in the malicious installer” continues the report.

The experts noticed that the second-stage payload containing the spyware is only served to users from China.

The spyware is able to gather system information and support data exfiltration capabilities. It is able to retrieve the list of installed software and running processes, Google Chrome and Edge histories, victims’ WeChat and QQ account IDs, the SSIDs and MAC addresses of Wi-Fi networks to which the victims are connected, and also allows operators to run arbitrary shell commands on the victim machine.

Experts believe the OnionPoison campaign is not financially motivated because threat actors did not collect credentials or wallets.

“In this campaign, the attackers use anonymization software to lure targets. Placing a link on a popular YouTube channel makes the malicious Tor Browser installer appear more legitimate to potential targets.” concludes the report. “Curiously, unlike common stealers, OnionPoison implants do not automatically collect user passwords, cookies or wallets. Instead, they gather data that can be used to identify the victims, such as browsing histories, social networking account IDs and Wi-Fi networks.”

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Pierluigi Paganini

(SecurityAffairs – hacking, Tor Browser)

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