(REUTERS) - Computer systems containing the Wall Street Journal's news graphics were hacked by outside parties, according to the paper's publisher Dow Jones & Co.

The systems have been taken offline to prevent the spread of attacks, but Journal officials have not found any damage to the graphics, the newspaper said citing people at the Wall Street Journal familiar with the matter.

A hacker who goes by the Twitter handle of w0rm allegedly posted tweets and screenshots claiming to have hacked the Journal's website and offered to sell user information and credentials needed to control the server.

Representatives for Dow Jones were not immediately available for comment.