SAN DIEGO — Undercover agents who posed as college students to bust more than 100 suspected drug dealers at San Diego State University never had to crack a book to gain acceptance on campus. All it took was cash.

The federal agents went to one or two parties but never actually went to class or lived in the dorms. Instead, they arranged meetings with suspected dealers and asked about buying cocaine, Ecstasy, methamphetamine, and other drugs, authorities said yesterday.

“All it took was saying, ‘Hey, I go to State, can you hook me up?'” a San Diego County prosecutor, Damon Mosler, said. “And then it was off to the races.”

The day after the drug sweep landed members of three fraternities in jail and led to the suspension of six fraternities, investigators disclosed how easy it was to penetrate the university’s drug culture.

Students who had gotten caught for drinking, minor drug offenses, or other crimes quickly turned informants and used text messages to introduce their drug dealers to undercover agents. Dealers made handoffs in front of dorms, in parking lots, or behind frat houses, sometimes in broad daylight in full view of surveillance cameras.

They apparently made little effort to launder their spoils. One fraternity brother arrested Tuesday drove his Lexus directly from a $400 cocaine sale on campus to a bank, where he deposited the cash, according to court papers.

That came as a surprise to agents from the Drug Enforcement Administration, who were used to being thoroughly screened by dealers scared of being arrested.

“They never gave any thought that we could be doing an operation there,” a spokeswoman for the DEA office in San Diego, Eileen Zeidler, said.