(August 25) - It's a routine response to nearly every terror attack. A suicide bomber blows himself to smithereens in an Israeli bus, marketplace or cafe, and a closure is clamped on all Palestinians in the West Bank and Gaza Strip. Palestinians resent it because about 100,000 of them are kept from earning livelihoods in Israel. But the Israeli public feels a tad more secure, believing that security forces will have an easier time keeping terrorists away.

Israeli and Arab experts are beginning to question the closure's effectiveness. Observers point out that the closure often doesn't even work since many Palestinians manage to bypass roadblocks, sometimes even under a soldier's gaze.

Ironically, the closure may be hitting hardest at the moderate Palestinians, those who passed security muster to obtain work permits. Many tend to obey the IDF and stay home because they would rather avoid risking a run-in with a border policeman and end up having their permit pulled.

Yet the Palestinians who pose a greater threat to Israel - those never issued work permits for security reasons - are the ones who try to infiltrate the roadblocks, in many cases successfully.

Resentment festers among Palestinians with permits who watch as those lacking the documents return home daily with cash in hand. Many workers couldn't even pick up their July paychecks since the Mahaneh Yehuda bombings came on the 30th, a day before payday.

"The black-market workers come to work as usual, but legal workers cannot," said Mohammed Amer, who works for Kav Le'oved (Workers' Hot Line), an Israeli organization devoted to the rights of Palestinian and foreign workers.

Amer said that sometimes a steady stream of Palestinians can be spotted infiltrating from the Kalkilya area, not far from the Abu Sneineh roadblock.

Sometimes lax enforcement of the closure is humane, as in the case of a young Palestinian mother who recently managed to evade checkpoints between Jenin and Jerusalem to fetch her baby from Makassed Hospital.

Other times it isn't. Tragically, three Jericho residents convicted of murdering taxi driver Shmuel Ben-Baruch last week apparently also skirted a roadblock to enter Jerusalem without permits.

Oren Shahor, former government coordinator for the West Bank and Gaza, presided over several closures in the past three years but questions their effectiveness.

"From a security standpoint we have to see things in a wider context," Shahor told Israel Radio. Instead of strengthening security, "we are actually achieving the opposite," he said.

Some officials are concerned that the extremists gain an upper hand during closures. They feel the government's decision to withhold tax money from the Palestinian Authority and a stepped-up campaign of demolishing illegally built homes, could be fueling resentment and enhancing sympathy with Islamic extremists, instead of helping Israeli security.

David Bar-Illan, director of communications for Prime Minister Binyamin Netanyahu, reasoned that much of the money went to pay Palestinian police officers suspected of involvement in attacks on Israelis. But the PA also needs to pay its police to conduct the crackdown on terrorism that Israel demands.

Brig. Gen. Salim Bourdine, deputy head of the West Bank and Gaza civil police force, noted yesterday that prime minister Yitzhak Rabin used to compensate the PA during closures to show that the measure was for security and not punishment.

"Unlike Netanyahu, Rabin used to compensate us for losses during closures," Bourdine said. He recalled two Israeli payments to the PA of $15 million and $20m. made during closure periods.

This is what PA chairman Yasser Arafat has sought to point out, but his warnings sometimes get lost in the combative rhetoric he spews out in speeches, such as a call this week to his people to prepare for a battle, "as we swore when we fired the first bullet for Jerusalem."

The statement was loosely translated by most Israeli media as a call to armed struggle, a strategy Arafat was supposed to have ditched when he made peace with Israel in 1993.

Few Israelis actually understood that Arafat's main point was that he wanted to release Israel's stranglehold on PA tax money.

Another potential consequence of the closure is a threatened Palestinian boycott of Israeli products, which could cost the Israeli economy tens of millions of dollars daily in lost revenues, or some $2 billion a year.

The boycott called this week is reminiscent of the repeated general strikes and attempts at blockading Israeli goods that took place during the intifada. More ominously, it signals another backslide into the pre-Oslo agreement era and more of a rapprochement between the PLO and Hamas. Hamas has called for boycotting Israel since 1991, and at the time, Fatah opposed the strategy.

But Israel's persistent closures after bombings seem to make many Palestinians feel like they're back in intifada times.

Already there are indications that the boycott is being observed.

"Today we returned Israeli fruit, appliances, toys, dairy products and frozen meat," Hisham Dasouki, a Palestinian security chief at the Karni crossing point into the Gaza Strip, told the Ramallah-based daily Al-Ayyam Monday.

Palestinian customs officials are also carrying a list of banned Israeli goods. Explaining the boycott, one Palestinian scientist said that the message from Oslo had been economic interdependence between the Palestinians and Israel, and globalization.

"Now that Israel is changing the game,we must too," said Jad Izhak, a food biologist in Bethlehem, who says he was arrested during the intifada for writing a handbook teaching Palestinians to grow vegetables in window boxes instead of buying from Israel.