FBI Director William Webster said yesterday he is confident that a series of sniper attacks on blacks -- including the shooting last May of civil rights leader Vernon Jordon -- ended with last month's arrest of Joseph Paul Franklin.

A 30-year-old drifter from Alabama who allegedly boasted of his membership in the Ku Klux Klan, Frankin was apprehended in Florida Oct. 28 on federal charges stemming from the slaying of two black youths in Salt Lake City.

Webster, speaking guardedly at a wide-ranging press conference, said he did not mean to suggested that the FBI has any evidence tying Franklin to the shooting as well. But he emphasized that "that was a significant arrest."

Franklin's apprehension at a Lakeland, Fla. blood bank was mentioned by the FBI director in a discussion that lumped together the Jordan shooting, the Salt Lake City killings and several other sniper attacks over the past year in Ohio and Indiana.

"We have one person in custody," Webster said after citing those incidents.

"It wouldn't be appropriate for me to be making accusations other than that with which he's charged, but I'm confident that that belt of activity will stop. All of these things feed on each other."

Webster added that the FBI has a number of Ku Klux Klan klaverns under an active investigation in connection with this same "belt of crimes."

Franklin is currently in federal custody in Utah as a result of the Aug. 20 murders of Theodore Fields, 20, and his friend, David Martin, 18, as they were jogging out of Salt Lake City's Liberty Park with two young white girls they knew.

Jordon, the president of the National Urban League, was shot in the back May 29 in the parking lot of a Fort Wayne, Ind., motel as he emerged from a car driven by a white woman member of the local Urban League's board of directors.

Webster said Franklin "has not been eliminated as a possible suspect." An FBI spokesman said later that the bureau was still trying to resolve where Franklin was the night Jordon was shot.

Meeting with reporters for an infrequent conference at FBI headquarters here, Webster also said he was satisfied that "we can do our job effectively" under four-year-old Justice Department guidelines that were designed to curb abuses in domestic security investigations.

The Heritage Foundation, a conservative Washington research group, called on President-elect Ronald Reagan this week to recognize "the reality of subversion" and revoke many of the restrictions.

Webster said he thinks the rules have "functioned well for the bureau" and "given us great confidence."

At the same time, the FBI director confirmed that he has been trying to allay the concerns of Senate conservatives about the rules for domestic security investigations laid down in a proposed legislative charter for the FBI. But he said he would describe the changes in store as "clarifications" rather than "concessions."

An intensive Justice Department investigation of news leaks about the Fbi's Abscam investigation has been completed and calls for disciplinary action against a number of FBI agents and Justice Department officials. Webster said, however, that he must resolve some complicated issues involving the use of polygraph tests before taking any action.

Asked about his own tenure in the Reagan administration, Webster noted that he is serving a 10-year term but said he would not insist on holding onto his post if a change were desired. He added, however, that he hasn't had any indication yet that he isn't wanted.

"I don't think they [Reagan transition officials] consider the FBI to be one of their immediate problems," Webster said.

Asked about the FBI's screening of some 130,000 Cuban refugees, Webster said it had been fruitful both in helping to identify some who had been sent here as spies and in helping to turn up sources useful for counterintelligence purposes. "Both avenues were explored and both have produced results," the FBI director said.