Online gambling sites have come under a fresh wave of distributed denial of service (DDOS) attacks by malicious programmers looking for a quick payday.

Over the weekend, the Twitter helpdesk of UK-listed operator Betfair reported that both its betting exchange and fixed-odds sportsbook were down for the count. On Monday, Betfair revealed that it was “currently experiencing a DDOS attack on our site, which is stopping all site traffic.” Later messages confirmed that the site’s issues were the result of “a deliberate attempt by a third party to interrupt our service.”

By late Monday, Betfair was reporting that its site was “stable for now, however we are still monitoring to see if this malicious activity re-occurs.” However, as of Tuesday, the site said it continued to experience “technical issues beyond our control” that were affecting its in-play feed.

Traditionally, DDOS attacks on online sportsbooks are timed to coincide with marquee sporting events, in the hopes that operators will consider a ransom payment an unwanted but worthwhile expense in order not to miss out on significant betting volumes. Betfair’s unknown assailants appear to have timed their attacks around this weekend’s Grand National racing fixture and Sunday’s climax of golf’s Masters event.