"Israeli statistics indicate that the barrier has substantially reduced the number of Palestinian infiltrations and suicide bombings and other attacks on civilians in Israel and in Israeli settlements, and Israeli officials assert that completion of the barrier will make it even more effective in stopping these attacks since "An absolute halt in terrorist activities has been noticed in the West Bank areas where the fence has been constructed". Israel's state comptroller, however, notes that most of the suicide bombers crossed into Israel through existing checkpoints.
Israeli officers (including the head of the Shin Bet) quoted in the newspaper Maariv have said that in the areas where the barrier was complete, the number of hostile infiltrations has decreased to almost zero. Maariv also stated that Palestinian militants, including a senior member of Islamic Jihad, had confirmed that the barrier made it much harder to conduct attacks inside Israel. Since the completion of the fence in the area of Tulkarm and Qalqilyah in June 2003, there have been no successful attacks from those areas. All attacks were intercepted or the suicide bombers detonated prematurely. In a March 23, 2008 interview, Palestinian Islamic Jihad leader Ramadan Abdallah Shalah complained to the Qatari newspaper Al-Sharq that the separation barrier "limits the ability of the resistance to arrive deep within [Israeli territory] to carry out suicide bombing attacks, but the resistance has not surrendered or become helpless, and is looking for other ways to cope with the requirements of every stage" of the intifada.
However, there is debate over how effective the barrier has been in preventing other attacks. A report by the Shin Beit, published in early 2006 notes that attacks in 2005 have significantly decreased due to increased pursuing of Palestinian militants by the Israeli army and intelligence organizations, Hamas's increased political activity, and a truce among Palestinian militant groups in the Palestinian Territories. According to Haaretz the report also mentions that "The security fence is no longer mentioned as the major factor in preventing suicide bombings, mainly because the terrorists have found ways to bypass it." Former Israeli Secretary of Defence Moshe Arens claims that the reduction in Palestinian violence is largely due to the IDF's entry into the West Bank in 2002."
http://en.wikipedia.org/wiki/Israeli_We … i_security