They're the ones who buy insurance on old buildings and later burn them down. No one knows exactly how many of them there are, or how much profit is made from the arson they practice, but estimates of annual property damage from arson in general range from $1 billion to $10 billion.

For years and for a variety of apparently logical reasons, cracking down on those who commit arson for profit has had low priority with most law-enforcement agencies. Lines of jurisdiction between police and fire departments never have been clear. Other crimes have long been considered more serious. And arson cases, often lacking witnesses and hard evidence, have been notoriously tough to prove. Nationally, the conviction rate in arson cases is less than 1 percent.

But there are increasing signs that awareness of arson, both of seriousness of the problem and of the need to find more effective ways to curb it, is growing:

Insurance companies, long criticized for dragging their feet and for frequently raising premiums rather than resisting claims, recently have spawned a number of industrywide organizations in an effort to improve investigations of suspected arson-for-profit cases.

Many cities and states have set up arson task forces with police, fire insurance, mayoral and public representation, for a more coordinated attack on the problem. Most experts in the field see this move as highly significant but complain that too often the membership of such groups is not broad enough and that, despite their value as a communication link, many go out of business after issuing one report or a set of recommendations.

More arson-for-profit cases are going to court and leading to more convictions. Thanks partly to the vigorous efforts of the recently formed Coordinating Council on Arson for Profit and a local program offering a reward for tips leading to the capture of arsonists, the number of arson-for-profits fires in Chicago dropped sharply in 1980, and the conviction rate in Cook County arson cases taken to court reached an unusually high 63 percent.

In the eyes of some experts, the lack of reliable national date on arson for profit remains a serious roadblock to countering it effectively. Many such fires are written off as "of undetermined origin," and fire departments and insurance companies keep such widely varying records that no national tally is considered trustworthy. To some extent, moving the crime's status up a notch on the federal level, to a major crime or felony under the FBI reporting system -- as a bill sponsored by Sen. John Glenn, (D-Ohio),? would do -- could improve the statistics gathering.

Insurance companies bristle at criticism that they have been less than vigorous in the fight against arson for profit. They insist their hands have been tied by restrictive laws that require them to pay even suspicious claims promptly or be sued; to insure even the most risky property; to give long advance notice before canceling any insurance policy, and which leave them liable to prosecution for sharing information on suspicious fires with law-enforcement agencies.

Accordingly, they are working for changes in these laws even as they try to attack the problem through new organizational efforts.

One relatively new industry activity widely regarded as promising is the Property Insurance Loss Register (PILR) in New Jersey. Through a computer file it can quickly cross-check property date to show any pattern of losses.

The Alliance of American Insurer's Property Loss Research Bureau (PLRB) in Chicago is working to improve the training of claims adjusters. While not professional investigators, adjusters often are the first company representatives on the scene, and their reports usually determine whether the company will probe the fire further.

Although sharply critical of the insurance industry for what he sees as paying "lip service," rather than action-based attention, to the problem, Dr. Charles Sisson of Battelle Memorial Institute's Center for Arson Prevention Training and Analysis calls the PLRB training move the industry's "first real thrust forward that makes sense."

Still another industry effort to crack down on fraud in general, including arson for profit, is the Insurance Crime Prevention Institute (ICPI). It works as an industry liaison with law-enforcement agencies, supplying them with file material on suspicious claims.

While everyone agrees that legal restructions do make the insurance industry's task of cracking down on arson more difficult, some arson experts argue that insurance companies can and should do more to prevent such crimes in the first place.

A proposal that could strengthen the industry's prevention role is a requirement in the Glenn bill that private insurors, before using a FAIR (Fair Access to Insurance Requirements) plan policy, get an evaluation of the property and share this specific information (where appropriate) with law-enforcement agencies. CAPTION: Picture, Estimates of annual property damage from arson range from $1 billion fo $10 billion. By Larry Morris -- The Washington Post