LONDON (AP) — A record-breaking cyberattack targeting an anti-spam watchdog group has sent ripples of disruption coursing across the Web, experts said Wednesday.

Spamhaus, a site responsible for keeping ads for counterfeit Viagra and bogus weight-loss pills out of the world’s inboxes, said it had been buffeted by the monster denial-of-service attack since mid-March, apparently from groups angry at being blacklisted by the Swiss-British group.