Finding who is responsible for an online threat aimed at Otago University that put the campus on high alert could be virtually impossible, according to internet security experts.
Students and staff at the university were on high alert this morning after a threat to carry out a shooting at the campus was made online.
The threat was posted anonymously to online forum 4chan on Monday night, but was deleted soon after.
Since then two other threats have been made to Victoria University and Massey University, but it was not known whether they were linked.
A part of Massey University's Palmerston North campus was evacuated this afternoon after a note was found threatening staff, and before that Victoria University's Murphy Building was evacuated after a note threatening the detonation of a bomb was found.
NetSafe executive director Martin Cocker said the Otago case had highlighted how easy it was for people to make such threats.
"The thing that this highlights is how easy it is for someone to use technology to post some information, or a threat, and then to create a whole lot of work for other agencies and a whole lot of damage," he said.
"It's incredibly easy, you can jump on a forum just about anywhere in the world and post a threat and people have to decide how credible they think that threat is and what actions to take in response to it. So for a few minutes of activity, you can create hundreds of thousands of dollars worth of work for other agencies."
Mr Cocker said because the threat was made through an American channel, as 4chan was founded in America, it would make it difficult for police here to track the culprit down.
"There is the option to for law enforcement to work with that company to find out who it is that placed the post but it is an expensive process, so they have to decide whether it warrants that cost and resource investment."
This was not the first time threats had been made on the forum, Mr Cocker said.
The New Zealand Council for Civil Liberties' spokesperson for computer and technology issues, Thomas Beagle, said it was very easy for people to remain anonymous on the internet if they wanted to, especially if they were using an overseas site.
"If you post [something] on a New Zealand site, the New Zealand Police can come and talk to the people who run the site and see what information they can find out, but if you post it on an overseas site, there's very little chance for police to find out that information," he said.
"4chan is an anonymous site. I mean the whole idea of it is not to identify yourself and 4chan doesn't keep any information about whose posting there."
Mr Beagle said while he expected this threat, and similar ones, were unlikely to be credible, police needed to take them seriously regardless.