This reduces the window of vulnerability during day zero of an attack.

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Hackers infected banner ads run by marketing firms such as Germany's Falk Esolutions, causing users who visited certain Web sites displaying Falk ads to download a Trojan horse that steals credit card numbers by exploiting yet another undetected vulnerability in Microsoft's Internet Explorer (a zero-day attack, once again).

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While some customers use this to overcome problems they have with enforcing vulnerability and patch management policies it is a cumbersome technology that does nothing to address new threats, zero day vulnerabilities, or insider attacks.

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