Brian Krebs:

According to Guilmette, whoever Dan is or was at Gtacs.com, he got his account compromised by some fairly inept spammers who evidently did not know or didn’t care that they were inside of a U.S. defense contractor which specializes in custom military-grade communications. Instead, the intruders chose to use those systems in a way almost guaranteed to call attention to the compromised account and hacked servers used to forward the junk email.
 
 “Some…contractor who works for a Vienna, Va. based government/military ‘cybersecurity’ contractor company has apparently lost his outbound email credentials (which are probably useful also for remote login) to a spammer who, I believe, based on the available evidence, is most likely located in Romania,” Guilmette wrote in an email to this author.
 
 Guilmette told KrebsOnSecurity that he’s been tracking this particular pill spammer since Sept. 2015. Asked why he’s so certain the same guy is responsible for this and other specific spams, Guilmette shared that the spammer composes his spam messages with the same telltale HTML “signature” in the hyperlink that forms the bulk of the message: An extremely old version of Microsoft Office.