College slackers, meet Patrick Murphy. A paralegal by trade, he is a book detective, an investigator who’s busiest close to midterms and finals weeks.

Employing some of the tactics used to stop drug dealers and illegal DVD peddlers, Mr. Murphy and other “enforcement associates,” as they’re called by his employer, John Wiley & Sons, have a more erudite target: pirated books and the ultra-secret teachers’ editions of textbooks that contain homework answers and test questions.

Mr. Murphy estimates he spends 50% of his workday on the Web hunting book bootleggers. When he finds a suspect, he’ll initiate a clandestine “buy.”

“You make the buys to have evidence,” Mr. Murphy said from John Wiley’s offices in New Jersey. Mr. Murphy will confront bootleggers with that evidence, offering them the choice of ceasing and desisting or facing litigation.

Mr. Murphy and his counterparts aim to rid academia’s hallowed halls of the so-called instructors’ solutions manuals to titles such as “Big Java,” “Multivariable Calculus,” and “Elementary Differential Equations and Boundary Value Problems, Seventh Edition.”

Publishing houses say they have no estimates of how many answer keys are available for sale via the Internet. A quick search through Web sites where textbooks are available — ranging from eBay to Amazon.com to abebooks.com, where one accused bootlegger sued last week in Manhattan Federal Court is said to do business — shows an electronic oasis for slackers seeking test questions and homework answers.

This point-and-click ease has presented new problems for publishers, who say there is a renewed need to police the Internet for covertly sold teachers’ editions, which are usually scanned and sold as PDF files, then e-mailed or sent via the postal service on a burned CD.

“In the old days, you’d have to stand at a photocopier and copy page by page,” Mr. Murphy said.

Because these contraband textbook transactions initiated by the enforcement associates involve the metro area, New York City is a nexus of publishers’ anti-cheating efforts. Some cases find their way into Manhattan Federal Court, where particularly flagrant sellers who ignore the publishers’ cease-and-desist letters find themselves served with lawsuits.

An investigation of abebooks.com involving a Texas bookseller, Lei Zhang, and his company, Harvard Book, made its way to the federal courthouse last Wednesday. Four big textbook publishers — Pearson Education, John Wiley & Sons, Thomson Learning, and the McGraw-Hill Companies — are asking a judge to force order Mr. Zhang and the five other alleged infringers to take the answer books off the Internet and turn over their profits.

“Professors use instructors’ solutions manuals to aid in grading homework,” a lawyer for the textbook publishers wrote in a filing to Judge Richard Casey. “Students, however, use instructors’ solutions manuals to cheat.”

Publishers say professors are less likely to adopt books if answer keys are widely available to students.

A man who answered the phone at a Richardson, Texas, address registered to Mr. Zhang first confirmed he was named Lei Zhang but disconnected the call after retracting his identity when The New York Sun sought comment about the publishers’ lawsuit.

John Wiley was the only party to last week’s joint lawsuit — which charges copyright infringement, trademark infringement, trademark counterfeiting, and common law unfair competition — to allow one of its enforcement associates to speak publicly about the job. Pearson and McGraw-Hill declined, and Thomson didn’t respond to a request.

Mr. Murphy estimates he sends out hundreds of cease-and-desist letters each year, and that less than a dozen end up in court. Still, those that do can result in settlements as high as “five figures.”

The chief higher education official of American Association of Publishers, J. Bruce Hildebrand, said the industry has trouble quantifying the problem. “We know that it involves millions and millions of dollars.”

Mr. Murphy wouldn’t discuss the specifics of the investigation that led to last week’s lawsuit against Mr. Zhang, but he said he follows the same investigative procedures no matter who he’s tracking.

One tactic he employs when making a buy is using his own home as the billing or shipping address for the bootlegged books.

“Certainly, you’re going to raise a red flag if I give my name and my title and my work address,” he joked, but he’s modest about his trade. “It’s not exactly cloak-and-dagger stuff by any stretch of the imagination.”