Microsoft DNS Server - DNS Zone Transfers from high ports (DNS_Zonexfer_High)

About this signature or vulnerability

RealSecure Network, BlackICE Agent for Server, RealSecure Desktop Protector, RealSecure Server Sensor, Proventia Server IPS for Microsoft Windows technology, BlackICE Server Protection, RealSecure Sentry, RealSecure Guard, BlackICE PC Protection, Proventia Server IPS for Linux technology, RealSecure Desktop Protector 3.6, Proventia Network IPS, Proventia Desktop, Proventia Network IDS, Proventia-G 1.1 and earlier, Proventia Network MFS:

This signature detects a zone transfer occurring from a source port greater than 1024.

This signature replaces DNS_Zone_High_Port.


Default risk level

Low risk vulnerability  Low

Sensors that have this signature

RealSecure Network: 7.0, BlackICE Agent for Server: 3.6, RealSecure Desktop Protector: 3.6, RealSecure Server Sensor: 7.0, Proventia Server IPS for Microsoft Windows technology: 1.0.914.0, BlackICE Server Protection: 3.6.cbd, RealSecure Sentry: 3.6, RealSecure Guard: 3.6, BlackICE PC Protection: 3.6.cbd, Proventia Server IPS for Linux technology: 1.0, RealSecure Desktop Protector 3.6: baseline, Proventia Network IPS: 2.0, Proventia Desktop: 8.0.614.1, Proventia Network IDS: A Series, Proventia-G 1.1 and earlier: G Series, Proventia Network MFS: 1.0, RealSecure Desktop: baseline

Systems affected

Various vendors Any application, DNS DNS

Type

Pre-attack Probe

Vulnerability description

A DNS zone transfer that originates from a non-privileged port number (above 1024) suggests that the zone transfer is occurring between your DNS server and a DNS client program, such as nslookup. Zone transfers contain a list of the systems on your network. Such information could be useful to an attacker in performing an attack.

How to remove this vulnerability

Observe the source address, and watch for additional events originating at that address. Configure your DNS server to disallow zone transfers from systems other than the peer DNS servers it must participate with, or at least from non-privileged port numbers. If it is a standalone DNS server, disallow zone transfers entirely.

References

ISS X-Force
Microsoft DNS Server - DNS Zone Transfers from high ports
http://www.iss.net/security_center/static/1226.php