Microsoft, the US software giant, faces an uphill battle in its attempts to crack down on e-mail spammers, internet experts have said.
"It is a global issue, it needs a global solution, and taking 15 spammers to court in the US and Britain is not going to even barely impact on the spam problem," said Martino Corbelli of Surf Control, a UK-based company that makes e-mail filtering software.
Microsoft said on Tuesday it had filed lawsuits against 15 alleged spammers, accusing them of clogging its computers and those of its customers with more than two billion unsolicited e-mail messages.
Thirteen of the lawsuits were filed in Washington state, which has recently passed tough anti-spam legislation, while the remaining two were filed in the UK.
Finding the spammers
"Legislating against spammers is extremely difficult, because they can exist and spam you from anywhere in the world, and they don't have to be in the same place where they spam you from," said Mr Corbelli.
"All they need to do is find an e-mail server somewhere in the internet which is set as an 'open relay server', and there are many many thousands of these, especially in places like Asia, South Korea and China.
"There are ISPs (internet service providers) in Russia who are spam-friendly. So finding these people is one thing. You can't legislate against people you can't find."
Spam, which by some estimates accounts for half of all e-mail traffic, is increasingly being seen as a threat to the viability of the internet.
Huge volumes of spam messages can clog up e-mail in-boxes, drastically slowing corporate computer networks.
A high proportion of spam messages advertise pornographic websites, causing offence as well as inconvenience to individual e-mail users.
Microsoft, the world's biggest software maker, has been at the forefront of efforts to tackle the problem, forming an alliance with Yahoo, EarthLink and America Online earlier this year to come up with ways of defeating spammers.
At government level, several US states have passed, or are in the process of drawing up, tough legislation to crack down on spammers.
On the other side of the Atlantic, new European Union rules making spamming illegal are expected to come into force in October.