By Chris Morris
BBC Europe Correspondent
Digital privacy rules aimed at stemming the tide of e-mail "spam" have come into force across the European Union.
Member states must decide how to punish companies and individuals
The new rules require companies to gain consent before sending e-mails and introduce a ban on the use of spam throughout the EU.
The unwanted junk e-mails, which are collectively known as spam, now make up more than half of all e-mail traffic.
The European Commission says they cost European business nearly $3bn in lost productivity last year alone.
So what do you do about it? - You ban spam.
But of course it is not that simple. Most of the spam which hits Europe comes from abroad, particularly from the United States.
Concerted international action is needed. But there are signs that everyone is waking up to the scale of the problem.
Last week a court in California issued a huge fine against one spamming company, and the United States Senate has approved a bill banning spam in the US.
It hopes the House of Representatives will soon follow suit.
None of this will be a quick fix, but it is certainly a start.
The new EU rules also limit the ability of companies to use files known as "cookies", to gain information about people who visit their websites.
It is up to each member state to decide how to punish companies and individuals who break the new rules.
"The law is a key tool to strengthen consumer confidence in the internet and electronic communications, which is a prerequisite for the success of e-commerce," said EU Enterprise Commissioner Erkki Liikanen.