布林说，2009年底谷歌发现自己遭受了一场非常复杂的网络攻击时，谷歌仍在评估各项选择。

Brin said Google was still evaluating its options when it discovered it was struck by a highly sophisticated cyber attack in late 2009.

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评估为防止每种攻击要付出的代价。

Estimate the cost of preventing each attack.

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阻止攻击的效率是这部分评估的目标。

The effectiveness of blocking attacks was the goal of this component of the review.

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