If a person received an email from the US Department of Justice, he or she may believe that it was actually coming from that department. However, an article on The Register notes that these emails may be phony and it will try to install a malware on their computer.

The email instructs the recipient to download an attachment which contains a trojan according to MessageLabs and Websense.

These type of emails are called Spear phishing. According to The Register, a recent phishing occured. The Federal Trade Commission was involved in that other case.

Source: The Register