Social networking sites Twitter and Facebook were available again to users in New Zealand and the rest of the world last night after an attack by hackers earlier in the day.
The companies said they were targeted by so-called denial-of-service attacks.
Twitter, which lets users post short comments known as Tweets, said its service might be slow as it recovered. Facebook said it had restored full access.
Netsafe executive director Martin Cocker told the Weekend Herald that websites run from New Zealand were vulnerable to attacks such as those that heavily disrupted Twitter and Facebook.
Users of the social networking sites faced outages or delays after suspected "denial-of-service" attacks - in which hackers overwhelm a website's servers with communications requests - leaving millions unable to carry out their daily routines.
The attacks, which came a month after the White House website was targeted in a similar online assault, have underscored the vulnerability of fast-growing networking sites that have been heralded as powerful new political tools.
Mr Cocker said many denial-of-service attacks occurred every day, but most were launched by people without the means to do any real damage.
"A denial-of-service attack is literally bringing the website down ... as opposed to hacking a website trying to steal something from it.
"Increasingly they are of concern. As a country, we don't have a lot of infrastructure to deal with it.
"What it does do, for any business that is subject to a successful denial-of-service attack, is that you lose confidence in that business."
If Facebook and Twitter, for example, were constantly taken down by these attacks, people would move away from them, Mr Cocker said.
"Most small businesses in New Zealand ... have no particular technical capacity to defend themselves against a denial-of-service attack.
"[But] the main thing is that none of them are ... high enough profile targets."
Motives for denial-of-service attacks ranged from political to rabble-rousing to extortion, with criminal groups increasingly threatening to hobble popular websites that did not pay demanded fees, security experts told Reuters.
In a blog post, Twitter co-founder Biz Stone said the company preferred not to speculate about the motivation of the malicious attack on the site that made it inaccessible for several hours.
"Twitter has been working closely with other companies and services affected by what appears to be a single, massively co-ordinated attack."
Members of Facebook, the world's largest internet social network with more than 250 million active users, were delayed logging in and posting to their online profiles.
Like Twitter, Facebook said the problems appeared to stem from a denial-of-service attack.
Speculation swirled on the internet that other sites, including Google, had also come under attack, but those rumours could not be confirmed.
Twitter's new-found fame made it an easy target for hackers, said Steve Gibson, the president of internet security research firm Gibson Research.
Security experts said a single group could have been behind the problems on Twitter, Facebook and the other sites as hackers evolve their ability to attack multiple sites at once.
- Additional reporting: Bloomberg
Facebook, Twitter disrupted by hackers
New Zealand is vulnerable to social networking site attacks because of a lack of infrastructure. Photo / Dean Purcell
AdvertisementAdvertise with NZME.