119-4.txt

snort入侵检测规则文件2.4 Snort是众所周知的网络入侵检测工具

Rule: 

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Sid: 
119-4

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Summary: 
This event is generated when the pre-processor http_inspect
detects network traffic that may constitute an attack.

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Impact: 
Unknown. This may be an attempt to evade an IDS.

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Detailed Information:
Microsoft IIS servers are able to use non-ASCII characters as values
when decoding UTF-8 values. This is non-standard behavior for a
webserver and violates RFC recommendations. All non-ASCII values should
be encoded with a %. This event may indicate an attack against a web
server or at the least an attempt to evade an IDS.

No web clients encode UTF-8 characters in this way. This is most likely
a malicious request.

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Affected Systems:
	All Microsoft IIS servers

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Attack Scenarios: 
An attacker merely needs to encode a web request using this non-standard
format.

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Ease of Attack: 
Simple. Many exploits exist.

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False Positives:
None Known.

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False Negatives:
None Known.

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Corrective Action:
Check the target host for signs of compromise.

Apply any appropriate vendor supplied patches.

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Contributors:
Daniel Roelker <[e-mail]> 
Sourcefire Vulnerability Research Team
Nigel Houghton <[e-mail]>

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Additional References:

HTTP IDS Evasions Revisited - Daniel Roelker
http://docs.idsresearch.org/http_ids_evasions.pdf

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