Australian email marketing application developers Campaign Monitor warned on Tuesday that it had been the victim of a hacking attack over the weekend.

Unidentified miscreants broke into servers last weekend and accessed some accounts. These compromised accounts were used to send spam, using lists already in the account and those imported by miscreants.

Credit card details were held on the compromised server, but only in an encrypted form. The main impact of the attack is a backlog of email marketing campaigns, made worse by the blocklisting of Campaign Monitor's systems because of spam runs by the hackers who compromised its systems.

Quite how the attack was carried out remains unclear. Campaign Monitor said the attack was a "deliberate, planned and complex intrusion".

More details on that attack, and what Campaign Monitor is doing in its wake, can be found in a notice on its website here. Further questions can be posed via the firm's Twitter account. ®

Related stories

• PerlMonks suffers unholy hack (3 August 2009)
• Oz Firewall still standing after inconclusive filter trial (28 July 2009)
• IT jobs site urges password resets after hack attack (20 July 2009)
• ImageShack hacked in oddball security protest (13 July 2009)
• StrongWebmail holds up hands to hack, plots further challenge (10 June 2009)
• Twitter users hit by smut spam hack attack (9 March 2009)