We make security trust decisions all the time--for instance, when accepting or rejecting a digital certificate prior to downloading software. But can we know whether the software we download is truly safe?

Maybe not, as recent attacks against well-known open source software sites suggest. Both attacks were against the source code distributions of the products, not the binaries, and both took the clever step of compromising the build process, rather than the actual executable produced. The first attack was against OpenSSH, a popular open-source secure shell tool. The attacker appears to have planted modified sources on the OpenSSH FTP server. For a one- or two-day period, anyone who downloaded some versions of OpenSSH and built the sources was vulnerable; the attack code connected to a particular host over a port 6667.

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