Global Payment firm MasterCard (MA) said it is experiencing heavy traffic on its external corporate website -

"We are working to restore normal speed of service," MasterCard said in a statement.

Earlier on Wednesday, hackers forced down the website of the international credit card service, MasterCard.

The move is likely to be an apparent revenge by alleged Wikileaks supporters. In what they called "Operation: Payback", the anonymous hackers announced on twitter that they successfully brought down the MasterCard website with DDoS attacks. MasterCard had earlier severed ties with the whistle-blower site, suspending all payments to the organization. The website currently remains inaccessible.

On Wednesday, one user under the pseudo name of Anon_Operation, tweeted, "WE ARE GLAD TO TELL YOU THAT is DOWN AND IT'S CONFIRMED! #ddos #wikileaks Operation:Payback(is a bitch!) #PAYBACK." 

Announcing the termination of service, MasterCard spokesman Chris Monteiro said on Tuesday that the company's rules 'prohibit customers from directly or indirectly engaging in or facilitating any action that is illegal'.