Thousands of e-mails were sent to a chief constable in a bid to cripple police computers, his force have said.
Messages said the sender knew where Mr Todd and his family lived
About 2,000 messages an hour were e-mailed to Gtr Manchester Police Chief Constable Michael Todd on Thursday.
Some of the messages said the sender knew where Mr Todd and his family lived, while others purported to be from US president George Bush.
Police, who have launched an inquiry to track down the culprit, believe it was an attempt to disrupt their operations.
A force spokesman said on Saturday: "Greater Manchester Police has been subject to a cyber attack using e-mails in an attempt to disrupt our service to the public.
"However, safeguards in place were effective and prevented any disruption to the force."