Since January 1, the IDF, Israel Police and Shin Bet (Israel Security Agency) have arrested close to 80 Arabs from east Jerusalem on suspicion of involvement in terrorism. The figure represents a sharp increase over the previous seven years, when only 270 east Jerusalem Arabs were arrested. The numbers, released by the Shin Bet on Tuesday following the second bulldozer attack in Jerusalem, represent a growing terror trend among east Jerusalem Arabs, who, with blue identity cards, benefit from free access to Israel without inspections at checkpoints. On the other hand, the fact that bulldozers were used in the two most recent attacks in the capital demonstrate the difficulty these terrorists are having in getting their hands on more lethal materials such as explosives, machine guns or other weaponry, so that they resort to what is available - their bulldozers. While Jerusalem has known the occasional terror stabbing over the past few years, before the shooting attack in the Mercaz Harav Yeshiva in March in which eight students were killed, the last major attack in the capital was in 2004, when two border policemen were killed in a suicide bombing in the French Hill neighborhood. This has to do with the remarkable job the IDF Central Command and the Shin Bet have done in preventing terror infiltrations into Israeli cities. This is not due to any drop in motivation or attempts - as the rise in arrests in east Jerusalem shows - but has to do with the near-completion of the security barrier, as well as the operational freedom the IDF enjoys throughout the West Bank. Just two hours before the attack in Jerusalem, Shin Bet chief Yuval Diskin appeared before the Knesset's Foreign Affairs and Defense Committee to discuss recent trends in Palestinian terrorism. Diskin portrayed a gloomy picture of the situation in the Gaza Strip, noting the new range of Hamas's rockets - capable of reaching Kiryat Gat and Ashdod - as well as the work the terror group is doing in laying mines along the border fence. When asked, however, to discuss the first bulldozer attack in Jerusalem, on July 2, Diskin turned critical, noting that Israel lacked effective deterrence against such attacks, mainly due to the foot-dragging on the demolition of homes belonging to the perpetrators of the Mercaz Harav and first bulldozer attacks. Considering the dozens of construction sites throughout Jerusalem and the many Arabs who work on them, there is almost no effective way to prevent a lone attacker from deciding to turn his work tool into a killing machine except for deterrence. The failure to demolish or even seal the homes of the previous attackers is a mistake that, according to the Shin Bet, is enabling future attacks. Another problem the Shin Bet chief noted was the lack of coordination between the police and the IDF vis-Ã -vis operations in east Jerusalem refugee camps. One example is in Shuafat, where to this day it is unclear who is responsible for performing arrest raids - the Border Police or the IDF. What is needed, security officials said, is a daily presence of security forces inside these east Jerusalem neighborhoods and refugee camps - another step that would add to Israel's deterrence and cause a potential terrorist to rethink his plans.