February 13, 2018

Kaspersky Lab discovers zero-day vulnerability in Telegram messenger

Kaspersky Lab researchers have uncovered ‘in the wild’ attacks being carried out by a new piece of malware using a zero-day vulnerability in the Telegram Desktop app.

Woburn, MA – February 13, 2018Kaspersky Lab researchers have uncovered ‘in the wild’ attacks being carried out by a new piece of malware using a zero-day vulnerability in the Telegram Desktop app. The vulnerability was used to deliver multi-purpose malware, which depending on the computer, can be used either as a backdoor or as a tool to deliver mining software. According to the research, the vulnerability has been actively exploited since March 2017 for the cryptocurrency mining functionality, including Monero, Zcash and more.

Social messaging services are an essential part of connected life, providing an easier way to keep in touch with friends and family. At the same time, they can significantly complicate life if they suffer a cyberattack. Last month, Kaspersky Lab published research on advanced mobile malware known as the Skygofree Trojan, which is able to steal WhatsApp messages. Now, Kaspersky Lab’s latest research reveals in the wild attacks with a new, previously unknown vulnerability in the desktop version of another popular instant messaging service – Telegram.

According to the research, the Telegram zero-day vulnerability was based on the RLO (right-to-left override) Unicode method. It is generally used for coding languages that are written from right to left, like Arabic or Hebrew; however, it can also be used by malware creators to mislead users into downloading malicious files disguised, for example, as images.

Attackers used a hidden Unicode character in the file name that reversed the order of the characters, thus renaming the file itself. As a result, users downloaded hidden malware which was then installed on their computers. Kaspersky Lab reported the vulnerability to Telegram and, at the time of publication, the zero-day flaw has not since been observed in the messenger’s products.

During their analysis, Kaspersky Lab experts identified several scenarios of zero-day exploitation in the wild by threat actors. First, the vulnerability was exploited to deliver mining malware, which can be significantly harmful to users. By using the victim’s PC computing power, cybercriminals have been creating different types of cryptocurrency including Monero, Zcash, Fantomcoin and others. In addition, while analyzing a threat actor’s servers, Kaspersky Lab researchers found archives containing a Telegram local cache that had been stolen from victims.

Secondly, upon successful exploitation of the vulnerability, a backdoor that used the Telegram API as a command and control protocol was installed, resulting in the hackers gaining remote access to the victim’s computer. After installation, it started to operate in a silent mode, which allowed the threat actor to remain unnoticed in the network and execute different commands including the further installation of spyware tools.

The artifacts discovered during the research indicate Russian origins of cybercriminals.

“The popularity of instant messenger services is incredibly high, and it’s extremely important that developers provide proper protection for their users so that they don’t become easy targets for criminals,” said Alexey Firsh, malware analyst, targeted attacks research, Kaspersky Lab. “We have found several scenarios of this zero-day exploitation that, besides general malware and spyware, was used to deliver mining software – such infections have become a global trend that we have seen throughout the last year. Furthermore, we believe there were other ways to abuse this zero-day vulnerability.”

Kaspersky Lab products detect and block the exploitation cases of this discovered vulnerability.

In order to protect your PC from any infection, Kaspersky Lab recommends the following:

  • Do not download and open unknown files from untrusted sources;
  • Avoid sharing any sensitive, personal information in instant messengers;
  • Install a reliable security solution such as Kaspersky Internet Security or Kaspersky Free that detects and protects from all possible threats, including malicious mining software.

Learn more about the discovered zero-day vulnerability, including technical details, on Securelist.com.

About Kaspersky Lab

Kaspersky Lab is a global cybersecurity company that celebrated its 20 year anniversary in 2017. Kaspersky Lab’s deep threat intelligence and security expertise is constantly transforming into next generation security solutions and services to protect businesses, critical infrastructure, governments and consumers around the globe. The company’s comprehensive security portfolio includes leading endpoint protection and a number of specialized security solutions and services to fight sophisticated and evolving digital threats. Over 400 million users are protected by Kaspersky Lab technologies and we help 270,000 corporate clients protect what matters most to them. Learn more at www.kaspersky.com.

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Media Contact
Jessica Bettencourt 
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jessica.bettencourt@kaspersky.com