The targeted attack that exploited a previously unknown vulnerability in Adobe's Reader application last month was extremely focused on defense industrial base firms, and affected just a handful of systems, according to a company spokesman.

Fewer than 20 machines, spread across a number of firms in the defense industrial base, were ultimately targeted in the attacks, which took advantage of a previously unknown ("zero day") vulnerability in Adobe's Reader and Acrobat software and three year old proof of concept exploit code written by a security researcher, according to Brad Arkin, the Director of Product Security and Privacy at Adobe.