A vicious cyber-virus is crippling the FBI's computer and e-mail systems -- continuing to jam the G-men's vast communications network more than nine days after being first detected, The Post has learned.

As of Thursday, sources said, FBI agents were still unable to e-mail their counterparts in other intelligence and law-enforcement agencies, a crucial post-9/11 necessity.

"Since the beginning of the week ... the private server has been down, and we haven't been able to e-mail each other," one source said.

The revelation comes as President Obama is expected to announce today the creation of a White House "cyber-czar" post to coordinate computer security throughout the federal government and the private sector.

The malicious code, which first surfaced last Wednesday, also hit the U.S. Marshals Office, forcing it to shut down much of its system for several days, officials said.

• Click here to read more from the New York Post.

• Click here to visit FOXNews.com's Cybersecurity Center.

• Got tech questions? Ask our experts at FoxNews.com's Tech Q&A.