"Attackers...continue their efforts with a very slight modifications to the original themes," said Parkour.

The latest campaign baits the scam with the promise of a report titled "Blinded: The Decline of U.S. Earth Monitoring Capabilities and its Consequences for National Security" from the Center for a New American Security (CNAS), a Washington D.C. think tank.

In fact, CNAS offers that report as a free .

The emails are customized for each recipient, a common tactic in targeting attacks -- dubbed "spear phishing" by security experts -- and apparently are aimed at people associated with political and international affairs.

"Victims get a message from an address of a close associate or a collaborating organization/agency, which is spoofed," said Parkour. "The message is crafted to look like a subscription form offering to enter Gmail credentials to activate it."