Security researchers from Kaspersky revealed a Zero-day vulnerability in Telegram Windows client that abused by attackers in wild for installing malware and cryptocurrency miners. This Telegram Zero day vulnerability was notified to telegram and the vulnerability no longer occurs in Telegram’s products.
What is the Vulnerability?
The vulnerability resides in with how the windows telegram client handles the RLO Unicode character that used to manage with the languages written from left to right “Right to left override”.
With this vulnerability, attackers can send as js file and make the recipient sees an incoming PNG image file instead of a JS file.
According to Alexey Firsh Attackers can sent malware in a message, the JS file renamed as evil.js -> photo_high_re*U+202E*gnp.js and the *U+202E* is the RLO character.
While the file rendered in the extension remains same as .js but rendered in a screen as photo_high_resj.png.
Telegram Zero day Vulnerability Exploitation to install Malware and Miners
Attackers use this vulnerability in wide to take control of the victim’s system, they push downloader and uses the Telegram API as command protocol to control systems.
Researchers said loader may be designed to download another piece of malware, possibly a logger that would spy on the victim user.
Now the cryptomining attacks are in the boom, attackers using it to make money from their victims and all they need to do is running a mining client on victim computer.
Cryptomining attacks and the Cryptocurrency exchange attacks are at it’s peak, in the recent massive attack, the hijacked 4275 websites to inject Coinhive Monero miner including the websites of government authorities(ico.org.uk), NHS Foundation (nhs.uk), and uscourts.gov.
Researchers concluded saying it appears that only Russian cybercriminals were aware of this vulnerability, with all the exploitation cases that we detected occurring in Russia.
We don’t have exact information about how long and which versions of the Telegram products were affected by the vulnerability. What we do know is that its exploitation in Windows clients began in March 2017
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