"One of the concerns of an attack like this is that the attacker is using a relatively weak botnet of home PCs in order to build a much larger botnet of beefy servers in preparation for a future attack, " he wrote in a blog post.

BBC: Wordpress website targeted by hackers

"We know for sure the botnet was used in at least one attack on Paypal, " he said.

BBC: Anonymous Wikileaks supporters mull change in tactics

Matthew Prince, chief executive and co-founder of Cloudflare, said that the aim of the attack might have been to build a stronger botnet.

BBC: Wordpress website targeted by hackers