Still, the shield's effectiveness as a defense in cyber-warfare is far from clear: Bruce Schneier, the founder and chief technology officer of security firm BT Counterpane, argues that no single strategy can stop determined hackers.

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Journalism advocacy groups said they welcomed the renewed interest in protecting journalists, though the effectiveness of a shield law would depend on how it is written and how easily the Justice Department could override the protections, citing national-security concerns.

WSJ: White House Aims to Revive 'Media Shield' Bill

Guild Wars 2 has shields, but their use is limited to the skill bar and their effectiveness is snuffed out entirely by the fact that any shield skill requires a cool down.

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