Authorities blame Islamist militants for most of the attacks, which often target security forces.

Pro-Taliban militants often target security forces in the province.

They also target security forces to try to show the Shi'ite-led government is failing to stamp out violence.

Militants often target security forces, and Shi'ite and Sunni mosques, but attacks on major oil sites beyond pipeline bombings are rarer.

Islamic State militants fighting Iraqi forces in the north and west regularly target security personnel and Shi'ite civilians whom they consider apostates.

It usually targets security forces, although Christian worshippers are increasingly bearing the brunt.

They have mostly targeted security forces in remote areas with ambushes.

Islamist attacks, mainly targeting security forces, have risen sharply in Egypt since Mursi's overthrow.

The NSA's attacks against Tor included targeting security holes in the Firefox web browser.

If you're facing targeted security threats, your problems run deeper than spyware on your devices.

A lot of exploits rely on exploiting user behaviour rather than targeting security infrastructures directly.

More than 250 people have been killed in the violence, which has mostly targeted security forces.

The quick response to intelligence and targeted security measures could provide a partial template for future action.

There have been dozens of other attacks and kidnappings by undercover militants targeting security and military officials.

Wednesday's bomb raised the spectre of indiscriminate attacks targeting security forces and going beyond traditional targets in northern Sinai.

At least one big bombing took place each month in 2012, usually targeting security forces, government offices or Shi'ite Muslims.