Distributed denial-of-service (DDoS) attacks and web site hacks continued to plague firms through the second quarter of this year, according to new research from web app performance management firm Akamai.

The company's State of the Internet report (PDF) found that SQL injection and cross-site scripting attacks continue to be popular vectors for web site hacks, with .hk and .cn emerging as the most likely country top level domains (TLD) to be infected.

The most risky generic TLD was judged to be .info with 11.8 per cent of all sites tested rated 'red' or 'yellow'.

DDoS attacks continued to cause headaches during the second quarter, some of which lasted for up to a week, the report found.

"We're already seeing interesting patterns emerging since the first report," said regional manger for northern Europe, Malcolm Rowe. "Some organisations are not installing patches and fixes to problems that have been known since 2001, which is staggering."

There was also bad news for cloud computing firms, according to Akamai. Amazon and Slahsdot.org both experienced outages of several hours, although the causes were not disclosed.