Mas Selamat Kastari, a detainee linked to the militant group Jemaah Islamiyah, famously escaped from Singapore’s Whitley Road Detention Center. His disappearance became a prominent issue in Singapore's security landscape. Initially detained for his alleged involvement in terrorism and for plotting attacks against targets in Singapore, Kastari's escape shook the confidence of the government and its law enforcement agencies. The evasion was particularly notable, as it drew attention to the challenges of managing terror suspects and the effectiveness of the nation’s imprisonment and monitoring systems.

Kastari’s successful escape involved evading strict surveillance and limitations that were supposed to prevent such occurrences. It is reported that he had been moved to a maximum-security facility in anticipation of his eventual release. After his escape, Kastari managed to cross the border into Malaysia, where he allegedly received assistance from sympathizers of Jemaah Islamiyah, allowing him to remain hidden for over a year. During this period, numerous search operations were conducted, yet he managed to evade capture, raising significant alarm in both Singapore and Malaysia about potential lapses in security protocols.

His evasion emphasized the complexities of combating terrorism in Southeast Asia, where cross-border cooperation is often challenged by disparate regulations and law enforcement capacity. Ultimately, Kastari was captured in 2009. The incident led to a revision of Singapore's security measures regarding detainees, including increased surveillance and tightened protocols surrounding detention facilities, shaping the country’s approach towards counter-terrorism initiatives.