Seculert CTO Aviv Raff says a nasty piece of malware linked to widespread destruction and bank account plundering has become more dangerous with the ability to evade popular sandboxes.
Raff says the Dyre malware ducks popular sandbox tools by detecting the number of cores in use.
The known but effective and previously unused technique is enough to beat at least eight of the most widely used free and commercial kit, Raff says.
"If the machine has only one core it immediately terminates," Raff says in a post.
"As many sandboxes are configured with only one processor with one core as a way to save resources, the check performed by Dyre is a good and effective way to avoid being analysed.
"On the other hand, most of the PCs in use today have more than one core."
Dyre is linked to a variant Dyre Wolf that IBM said last month plundered some $1 million from bank accounts.
Raff informed the affected sandbox developers of the evasion technique.
Dyre's Upatre downloader also sports new evasion techniques including a different user agent and grammatical fixes previously used to identify the malware.
Raff says the technique proves sandboxing should not be used in isolation to stamp out malware.
It is the latest development in a long history of cat-and-mouse warfare between malware writers and white hat defenders.
Criminals need to contend with infiltrating victim machines while avoid anti-virus and white hats who look for indicators that are hallmarks of a type of malware.
Defenders meanwhile face malware that uses increasingly complex evasion techniques that are specifically honed to beat sandboxes, virtual machines and other tools. ®