You may laugh on me if you already knew, but maybe not
Patch XP, 7, 8, 8.1, 10 and SMB 2003 Server immediately to prevent from worm and ransomware WannaCry 3rd wave since friday. The actual version has no kill switch in the WORM, the ransomware is part two of WannaCry.
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So just patch your system.
The Yara Rule Set you find here
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The Indicators Of Compromise (IOC) you find here
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If you are interested in CyberSec Threat Intel Sharing standards you can learn these terms
STIX Structured Threat Information Expression
TAXII Trusted Automated eXchange of Indicator Information
CybOX Cyber Observable eXpression
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