The information published by antivirus developer Eset revolves around a Firefox browser extension, according to a report from Ars Technica. The extension purported to offer enhanced security, but in fact served to give the hackers a method of seizing control over an infected system.
A bit.ly URL directed the extension toward its command and control server, but the address was not actually present in its source code. Instead, it was hidden away in a seemingly random comment on one of Spears’ Instagram posts.
The extension would pore over each photo’s comments, computing a custom hash value for each string of text. When it found the comment with a hash that matched with the stipulated value of 183, it ran a regular expression — a sequence of characters that defines a search pattern — on the comment to translate it into the URL.
Eset researchers managed to discover a bit.ly URL hidden in this manner, which linked to a domain that has been used by Turla in the past.
The URL in question only received a small number of visits around the time when the Instagram post was published, which can be interpreted either as a sign that the malware is still being put through its paces, or that the attack was highly targeted.
Firefox developers are apparently in the process of tweaking the browser so that the current implementation of this attack won’t work in the future.
