In the few days since the World Trade Centre atrocity, it has become a clichΘ to suggest that things will never be the same again and that laws, rights, relationships and obligations will all have to be reassessed in this new world.

These changes may be difficult to predict but it is certain that the debate on the privacy of the individual and, in particular, how that right is protected online has been completely changed. Changes are already happening, more rapidly than may be realised, and these changes may have a considerable effect on privacy in the Republic and Europe.

The United States spends billions on its intelligence services but they were unable to warn of an attack that killed more people on US soil than any event since the American civil war.

The US maintains an extensive and expensive infrastructure for intercepting telecommunications. This activity is highly secret and those systems that have achieved greatest prominence may not necessarily be the systems that are most effective or useful.

The European Parliament has attached great significance to the "Echelon" spy system, which is used to intercept satellite communications by America's National Security Agency in conjunction with other countries, notably Britain.

The FBI has its "Carnivore" system (whose unfortunate name has been changed to DCS 1000), which is designed to intercept communications such as e-mail.

In many countries a warrant or other authority must be sought before intercepting an individual's communications.

In the Republic, the Minister for Justice must issue a warrant under the Interception of Postal Packets and Telecommunications Messages Act 1995, and his decisions are reviewed annually by a High Court judge.

The US has even stronger protections but, in the hours and days following the World Trade Centre attacks, FBI agents allegedly approached American internet service providers with requests and warrants to attach Carnivore technology to their systems.

The US's laws are changing to ease its controls and the US Senate passed emergency measures, two days after the terror attacks, which permit the placing of wire taps on computers and phones of people suspected in hijacking, bombing or other terrorist acts.

But US Attorney General Mr John Ashcroft wants Congress to go further and pass laws that extend electronic surveillance.

Instead of monitoring individual phones or e-mail accounts, Mr Ashcroft wants the law to attach to terrorist suspects themselves as opposed to their phones. This would be a response to the advent of the pre-paid mobile phones and internet cafΘs that enable a suspect to evade surveillance easily, frequently and cheaply by changing his phone number or electronic address.

Even if these laws change, the interceptions infrastructure may continue to be ineffective as terrorist groups are allegedly using very strong encryption to protect their communications from interception. Changes in the law may be sought to make the sale, distribution or use of such strong encryption programs illegal, reopening a debate on encryption controls that US law enforcement agencies appeared to have lost.

There is no question that communications sometimes have to be intercepted to protect the public and prosecute crime, but this need has to be balanced with the protection of the individual's right to privacy. This balancing act creates ambiguities in laws and legislation.

The attacks in New York and Washington have probably altered the point at which this balance will be made. It may be more difficult to argue against laws mandating interception or decryption, which may help to protect the world from terrorism on this scale.

But arguments can be made. The Echelon spying system focuses on messages sent via telecommunications satellites. Osama bin Laden is based in Afghanistan, a country ravaged by years of war. It is very likely that the only modern telecommunications available to him would be those that utilise satellites.

But Echelon appears to have given no warning of these attacks. The reason may be simple. Mr bin Laden does not make calls that he knows will be monitored, and systems such as Echelon are of no use where meetings take place face to face.

The sheer volume of electronic communication worldwide might also be a problem.

Although appalling and brutal, the destruction of the World Trade Centre, the attack on the Pentagon and the crash in Pennsylvania were not high-tech crimes. Advanced technology may prove just as ineffective at preventing future crimes as it did at averting this one.

Denis Kelleher is a practising Barrister and co-author of Information Technology Law in Ireland (Butterworths: Dublin). Website: http://www.ictlaw.com