Hackers are spreading the Chthonic banking trojan via legitimate-looking PayPal emails, security outfit Proofpoint has warned.
The emails are 'authentic' and don't trigger antivirus warnings because they come via PayPal from accounts that appear to be legitimate. "The sender does not appear to be faked. Instead the spam is generated by registering with PayPal (or using stolen accounts) and then using the portal to request money," said Proofpoint in a security advisory.
The attackers take advantage of a feature that allows users to include notes when sending money request messages. One sample picked up by Proofpoint showed that Gmail failed to block the email since it appeared to be legitimate. "PayPal's money request feature allows adding a note along with the request [and] the attacker crafted a personalised message and included a malicious URL," said the advisory. "In a double whammy, the recipient here can fall for the social engineering and lose $100, click on the link and be infected with malware, or both."
Intriguingly, perhaps, Chthonic downloads a second-stage payload, a previously undocumented malware known as AZORult which the company is currently investigating. Fortunately the campaign seems somewhat limited at the moment, according to Proofpoint, perhaps partly owing to the overhead required in opening PayPal accounts or gaining access to compromised accounts. Google Analytics indicates that the URL of the malicious link, which uses a Goo.gl link, has been clicked only 27 times. PayPal has yet to comment on Proofpoint's findings.