Parts of the plot might remain undetected, Obama's counterterror chief warned.

白宫反恐负责人警告，该阴谋事件尚未完全侦破。

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This type of clot is known as a chronic subdural haemorrhage, and can remain undetected for some time.

这种类型的血块是已知的作为慢性硬膜下出血，并能保持未被发现了一段时间。

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Panda pregnancies can last anything from 11 weeks to 11 months and can remain undetected until shortly before birth.

大熊猫的妊娠时间能持续11周到11个月不等，甚至到产崽时也不容易被发现。

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This tactic fails too often because criminals are adept at obfuscating their attack code, allowing their activity to remain undetected for long periods of time.

FORBES: To Stop Cybercrime: Understand Crime Logic, And Adapt

The case has become a major embarrassment for Canada as its military and government struggle to explain how the former navy officer was able to use such primitive methods to copy and convey his material and remain undetected for so long, our correspondent adds.

BBC: Prison for Canadian navy officer turned Russian spy

What is more, the reunification of Germany presents special export control problems, given that the Chairman of the Volkskammer Commission to Control the Dissolution of the Stasi (East German KGB operatives and secret police) reported yesterday that at least half of the 2, 448 Stasi officers sent into German firms and institutions remain undetected.

CENTERFORSECURITYPOLICY: Center for Security Policy | Will Congress Restore US Technology Security? Export Controls�� Imminent Moment Of Truth