2033.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:
2033

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Summary:
A request has been made to rpc.ypserv from an external source that 
should not have access to this service. This may be indicative of an 
intelligence gathering activity as a prelude to a more serious 
compromise of system resources.

service against the target host.

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Impact:
Disclosure of sensitive system information to an unauthorized user.
Possible denial of service.

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Detailed Information:
The rpc.ypserv daemon queries information in the local NIS maps. A 
response to this query may divulge important information to the user 
performing the query. This could lead to futher exploitation of 
resources on the network.

In addition, a vulnerability exists in ypserv on some Linux platforms 
that could lead to a buffer overflow and root compromise of the target 
host. This is achieved by making a multitude of requests for a NIS map 
that does not exist.

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Affected Systems:
Multiple systems running versions of ypserv prior to 2.5.

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Attack Scenarios:
The attacker can craft a malicious request to rpc.ypserv such that 
valuable information can be returned to the attacker.

In the case of a buffer overflow, the attacker might issue a large 
therefore, be seen many times.

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Ease of Attack:
Simple

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False Positives:
None Known

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False Negatives:
None Known

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Corrective Action:
Disallow all RPC requests from external sources and use a firewall to 
block access to RPC ports from outside the LAN.

Upgrade ypserv to the latest version.

Use /var/yp/securenets to list the hosts allowed to access this resource
where appropriate.

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Contributors:
Sourcefire Research Team
Brian Caswell <[e-mail]>
Nigel Houghton <[e-mail]>

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Additional References:

Bugtraq:
http://www.securityfocus.com/bid/6016
http://www.securityfocus.com/bid/5914

CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1232
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-1043
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-1042

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