Abusive e-mails targeted at staff have also been commonplace, according to Huntingdon's IT director.
Huntingdon, which secured its financial future last month, has recently completed a security review with an outside consultancy. It has a double firewall system, including a filter and anti-virus software, at the centre of its IT security armour.
Huntingdon's IT director, who asked not to be named, managed to trace the origin of some abusive e-mails and forced Internet service providers (ISPs) to close down individual accounts.
"We are dealing with a loose coalition which comes together and has no charitable and legal status," the director said. "But we have been fairly successful in forcing ISPs to close down particular accounts."
Another tactic of animal activists has been to use the hidden meta tags in Web site code. The aim is to lure Web users looking for the official Huntingdon site to alternative protest sites.
One site found using a search engine and viewed by Computer Weekly carried the message "Welcome to Hell" under the company's name.
Huntingdon has taken legal action over the rogue Web sites but, according to a spokesman, the case is not always clear cut.