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Malware signed with the Adobe code signing certificate


Last week, Adobe released an advisory (APSA12-01) announcing the upcoming revocation of an Adobe code signing certificate as it was compromised and used to sign at least two malicious utilities. They identified a compromised build server that required access to the code signing infrastructure and have forensic evidence that links it to the signing of these malicious utilities. They have confirmed that the private key was not compromised and this build server was used to sign the malicious utilities using the standard protocol used for valid Adobe software.

As a member of the Microsoft Active Protections Program (MAPP), the MMPC and other members received information about this compromise and immediately deployed protection for our customers – Win32/Adbposer. One of the primary goals of this attack is to evade antivirus and other security products as most of them have a feature/optimization to trust binaries signed by trusted certificates. The MMPC removed the compromised certificate from our trusted certificate list right away. For your protection please ensure that your virus definition version is greater than 1.137.689.0.

The malicious utilities include a tool used to dump passwords and a malicious ISAPI filter. Following are the details of the samples:

SHA1: c615a284e5f3f41cf829bbb939f2503b39349c8d
Signature timestamp: Thursday, July 26, 2012 8:44:40 PM PDT (GMT -7:00)
Detected as PWS:Win32/Adbposer.A

SHA1: 934543f9ecc28ebefbd202c8e98833c36831ea75
Signature timestamp: Thursday, July 26, 2012 8:44:13 PM PDT (GMT -7:00)
Detected as PWS:Win32/Adbposer.A.dll

SHA1: fecb579abfbc74f7ded61169214349d203a34378
Signature timestamp: Wednesday, July 25, 2012 8:48:59 PM (GMT -7:00)
Detected as Trojan:Win32/Adbposer.B

Adobe has revoked the certificate today for all software code signed after July 10, 2012 and are also in the process of issuing updates signed using a new digital certificate for all affected products.

We have been tracking this issue very closely and the telemetry shows that this issue is not prevalent and is being used in highly targeted attacks only. We will continue to monitor for new malware leveraging this issue.

Tanmay Ganacharya

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