Manchester United say they had no option but to take legal action against an anti-Glazer protester who they allege posted details of 400 of the club's corporate clients on the internet.
The club are suing Thomas McKenna, of Greater Manchester, and have filed a writ at the High Court. United are asking the court to order McKenna to deliver up or destroy the data, to issue an injunction to prevent any repetition, and seeking damages.
United claim the data was stolen from them, though they do not know by whom, and then posted on a website used by supporters opposing the takeover of the club by the Glazer family in 2005.
The action led to companies on the list having property damaged and others receiving visits at their home address.
A United spokesman said: "The theft of data led to some of the companies named on the list having their property attacked and suffering significant personal distress.
"The club has a duty to demonstrate to all our fans that we will not tolerate that and will take action against the perpetrators. We take data security very seriously.
"Doing nothing was not an option."
It is understood United have no record of McKenna as being a season ticket holder or part of any membership scheme.Reuse content