Simmons & Simmons is set to become the first firm in the UK to link all of its IT systems and confidential information to an intranet.
Simmons has emulated the BBC and NatWest Global Markets by buying the US Web-based IT system Open Text Livelink for a "significant six-figure" investment.
By next summer, every document kept by the firm, including confidential client files, will be held on a series of Simmons databases linked to an intranet - effectively a private Internet.
The intranet will in turn be connected to the Internet, allowing clients limited access to the system.
Simmons is now piloting the cross-departmental system among 200 fee earners and is due to introduce it to 1,300 users across eight countries next summer.
Currently, the firm uses Novell's Soft Solutions document management system, which has not been guaranteed as millennium compliant.
Simmons IT director Chris Roberts said security measures such as passwords and firewalls were built into the system to "minimise the risk, wherever possible" of hackers breaking in. But he conceded he could not "guarantee the safety 100 per cent" of documents kept within the system.
He refused to reveal the full cost of Open Text Livelink but said it was a "significant six-figure sum".
Open Text marketing manager for Europe, Africa and the Middle East Neil Wilson pointed out that the system was already used by several "secretive" bodies, including US government agencies.
He claimed its weakest point would be the "administrative team" operating the software rather than hackers.
Internet security expert Nick Hutton, who is security product manager at leading Internet service provider UUNet, said that it would be much easier for people to physically break into a law firm at night and steal documents than to hack into a secure intranet system.
IT author and technology expert Richard Susskind, who predicted greater use of Internet tools by lawyers in his seminal book The Future of Law, said Simmons' new system was "precisely the kind of use of technology that clients repeatedly said they were interested in".
Susskind added that usual methods of transferring documents by courier did not guarantee safety and said firms had to make a "commercial decision" based on benefits for clients of superior technology against the security risks.