The criminals are using "spear phishing" tactics -- spam e-mails designed to get through spam blockers -- which are believed to be secure e-mails.

"Law firms have a tremendous concentration of really critical, private information," FBI cyber division chief Bradford Bleier told the AP.  Accessing the computer network proves to be "a really optimal way to obtain economic, personal security related information."

Since law firms have sensitive information about clients and other people the firm interacts with, there normally is a large client list available to criminals.  Specifically, firms negotiating large-profile cases in the United States and overseas are targeted by hackers that are based in foreign nations.

Cyber crime has become an increasingly troublesome problem the U.S. government and private sector companies are trying to deal with.  A large number of cyber attacks have originated from China and Eastern Europe, but western leaders are hesitant to blame other countries.

South Korea and the United States are blaming North Korea for a recent string of attacks against several nations.

Although some online criminal groups may be spearheaded by the Chinese government, without much proof, the U.S. government hasn't been as upfront about the issue as some analysts would like.  As Congress continues to demand President Barack Obama to pick a cybersecurity coordinator, cyber attacks are now being blamed for a Brazilian  power outage and the Swiss Ministry also suffered a cyber attack.