CERT-UA warns of malspam attacks distributing the Jester info stealer

Pierluigi Paganini May 09, 2022

The Computer Emergency Response Team of Ukraine (CERT-UA) warns of attacks spreading info-stealing malware Jester Stealer.

The Computer Emergency Response Team of Ukraine (CERT-UA) has detected malspam campaigns aimed at spreading an info-stealer called Jester Stealer.

The malicious messages spotted by the Ukrainian CERT have the subject line “chemical attack” and contain a link to a weaponized Microsoft Excel file. Upon opening the Office documents and activating the embedded macro, the infection process starts.

Government experts observed that malicious executables are downloaded from compromised web resources.

“The government’s team for responding to computer emergencies in Ukraine CERT-UA revealed the fact of mass distribution of e-mails on the topic of “chemical attack” and a link to an XLS-document with a macro.” reads the report published by CERT-UA. “If you open the document and activate the macro, the latter will download and run the EXE file, which will later damage the computer with the malicious program JesterStealer.” 

Jester Stealer

The Jester stealer is able to steal credentials and authentication tokens from Internet browsers, MAIL/FTP / VPN clients, cryptocurrency wallets, password managers, messengers, game programs, and more. 

The info-stealer implements anti-analysis capabilities (anti-VM/debug/sandbox), but it doesn’t implement any persistence mechanism. The threat actors exfiltrare data via Telegram using statically configured proxy addresses.

“Stolen data through statically defined proxy addresses (including in the TOR network) is transmitted to the attacker in the Telegram.” continues the report.

The report includes Indicators of Compromise (IoCs).

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Pierluigi Paganini

(SecurityAffairs – hacking, Jester stealer)

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