If you found your Internet surfing coming up slow in recent days, it’s possibly because of one of the biggest cyberattacks experts have ever seen.

A Dutch web hosting company called Cyberbunker allegedly launched a cyberattack against Spamhaus, a non-profit group that fights junk email. Spamhaus had blacklisted Cyberbunker for supposedly helping to spread spam – a claim Cyberbunker denies.

“The cybercrime underground has gotten to be this kind of business-driven, money-driven process,” says Alex Cox, a lead security researcher for the firm RSA. “And when people’s incomes are affected, they have the ability to really cause some problems if they want to.”

While Cyberbunker told Bloomberg News that it has never sent spam, it is a company that allows nearly any content to be hosted on its computers, with the exception of child porn and some terrorism related material.

Experts say the attack isn’t very sophisticated, but the mess points to a weakness in the architecture of the Internet:  when you type a web address into your device, the name goes to a kind of electronic phone book that looks up the computer it needs to find.

“Some of those ‘phone books’ are open for anybody to use,” says Paul Royal, a research scientist at the College of Computing at Georgia Tech. “Unfortunately that means that attackers can abuse those ‘phone books’ by asking a question in a way that generates a very large response and targets a victim of their choice.”

Professor Royal says there are techniques to make the Internet more resilient, but rolling them out universally would be expensive.