It won’t surprise many computer security experts, but the U.S. Homeland Security Department (DHS) has proven again that humans are the “weak link” in the data security chain.

In an effort to test computer security in federal agencies, DHS dropped thumb drives and CDs in the parking lots of various federal buildings and office buildings housing government contractors. Among the people who picked up the devices and disks,, 60 percent plugged the them into office computers. If the drive or CD case had an official logo, 90 percent were plugged in. Had they carried auto-loading malware, entire government networks might have been compromised.

A full report on the Homeland Security study will be published this year, according to Sean McGurk, director of the department’s National Cybersecurity and Communications Integration Center.