German officials on Friday defended a proposal to use ''Trojan horse'' software to secretly monitor potential terror suspects' hard drives, amid fierce debate over whether the measures violate civil liberties.

Interior Minister Wolfgang Schaeuble wants to include the measure in a broader security law being considered by conservative Chancellor Angela Merkel's coalition government.

Schaeuble defended the tactic in an interview with n-tv television Friday, calling the ongoing debate ''completely exaggerated,'' underlining that judicial approval would be required before the measures could be used. ''It's about a few isolated cases.''

Carried in e-mails that appear to come from other government offices, the software would allow authorities to investigate suspects' Internet use and the data stored on their hard drives without their knowledge.

Use of the government-produced technology for spying on terror suspects ''will cover a serious and scandalous hole in our information that has arisen through technical changes in recent years,'' Stefan Kaller, a spokesman for Schaeuble told reporters.

The proposal stems from a Federal Court decision earlier this year to block clandestine remote searches of suspect computers until there was a law governing the practice.

It has met with strong criticism from opposition parties and civil liberties groups.

Max Stadler, a security expert with the opposition Free Democrats, insists such practices would weaken citizens' trust in government.

''It is an invasion into the private sphere,'' Stadler told ZDF television.

Schaeuble's office has not yet released a copy of the bill, but elements of it that were leaked to German media include allowing investigators to send e-mail messages that appear to be from the Finance Ministry or the Youth Services Office, but which actually carry the Trojan horse software.

Thomas Steg, a spokesman for Merkel, said the chancellor supports the broader bill, but expects ''a difficult and intensive discussion with the ministries, the coalition and the experts'' on it before it is passed into law.

Hartmut Pohl, an expert with Germany's Association for Computer Technology, expressed doubt that the measure would succeed, pointing out that most suspects are technologically savvy enough to recognize and remove the Trojans from their hard drives.

The government has not released any details of exactly how the software would operate.

In February, Germany's Federal Court of Justice rejected federal prosecutors' attempts to search hard drives through the Internet. Prosecutors had argued that the legal reasoning used to allow telephone surveillance and other electronic eavesdropping techniques should also be applied to evidence gathering over the Internet.

Germany, unlike Britain or Spain, has been spared a major terrorist attack, but German and U.S. officials have warned recently of increased dangers, prompting tighter security measures.

In recent weeks, German troops and others working in Afghanistan have been targeted by Islamic radicals in suicide bombings and kidnappings aimed at forcing the withdrawal of the nation's 3,000 troops deployed with the international security force there.

The heightened threat level only makes the matter more urgent, Kaller said, insisting that, ''Any delay can mean a security risk.''