After the 2001 terrorist attacks, retired Federal Bureau of Investigation agent Michael Warren saw that many phone and Internet companies would need help meeting an expected jump in law-enforcement requests for customer calling and email information.

His prediction proved correct. Mr. Warren formed a company that won business from telecom, cable and Internet-service providers around the U.S. Last year, he sold the business for an undisclosed amount.

"There's been a significant increase in demand and pressure on companies for providing records, tracing calls and wiretapping," said Mr. Warren, now a vice president for fiduciary services at NeuStar Inc. of Sterling, Va., which bought his company. "That's led to a great deal of strain on carriers."

Often overlooked amid the controversy over the legality of the Bush administration's eavesdropping without warrants is a huge increase in recent years in the number of wiretaps conducted with court approval. Smaller telecom companies in particular have sought help from outsiders in order to comply with the court-ordered subpoenas, touching off a scramble among third parties to meet the demand for assistance.

VeriSign Inc., the communications company in Mountain View, Calif., that manages the Internet's .com and .net domain-name suffixes, entered the assistance business after the Sept. 11, 2001, terrorist attacks. SS8 Networks Inc., a San Jose, Calif.-based company, in 2001 morphed its business into one that helps others deal with law-enforcement requests, after starting as an Internet-phone-equipment company a couple of years earlier.

The number of telephone wiretaps from 2000 to 2004 authorized by state and federal judges increased by 44% to 1,710, according to the latest annual report from the Administrative Office of the U.S. Courts. The vast bulk of the wiretaps related to drug and racketeering investigations, according to the report. But terrorism and other national-security investigations also helped drive the increase, according to security experts and service providers.

CenturyTel Inc., a fixed-line phone company and Internet-service provider based in Monroe, La., serving 2.5 million customers, received about 1,500 subpoenas and court orders for customer data last year, said Stacey Goff, CenturyTel's chief legal counsel.

Almost 20% of those related to national-security matters, about double the percentage of such requests from a year earlier, he said. The overall number of requests from law enforcement for customer information has nearly doubled from about five years ago, Mr. Goff added.

"A few years ago it was drugs and divorces, that was it," said Mr. Goff. "Now, we're getting requests on more-sensitive matters."

Companies assisting carriers handling the increased law-enforcement demands typically sell software that simplifies the process of reviewing tens of thousands of phone-call records. Some third parties also provide assistance by setting up in-house compliance procedures, interacting with law-enforcement agencies and providing access to networks for wiretaps.

Smaller telecom, cable and Internet companies generally haven't received requests from the National Security Agency, the super-sensitive U.S. intelligence-gathering arm, for customer data without warrants, officials at smaller companies say. Such NSA requests -- which are at the core of the domestic eavesdropping debate -- have been aimed at large international telecom companies, which tend to handle government and law-enforcement matters in-house.

Big telecom companies in the U.S. were required under the 1994 Communications Assistance for Law Enforcement Act to install equipment to help law enforcement keep up with advances in technology, such as the rise of cellular, the switch to digital technology from analog and new features such as call forwarding.

Now, Internet providers must also comply with the act. The Patriot Act, passed after the 2001 terrorist attacks, took matters a step further, giving law-enforcement agencies powers to monitor individuals and all the ways they communicate, rather than being limited to a specific communication device.

Government surveillance has intensified even more heavily overseas, particularly in Europe. Some countries, such as Italy, as well as government and law-enforcement agencies, are able to remotely monitor communications traffic without having to go through the individual service providers.

To make it easier for authorities to monitor traffic, some also require registering with identification before buying telephone calling cards or using cybercafes.