Hi all,
Can someone please help to provide solutions for below security-related Linux server issue?

Level : 2 UDP Constant IP Identification Field Fingerprinting Vulnerability
Level : 2 TCP Sequence Number Approximation Based Denial of Service
Level : 2 Operating System Detected
Level : 2 Host Uptime Based on TCP TimeStamp Option

Currently we have two name servers and both also having the above same issue.
Thanks in advance for your help

Take each vulnerability, and search for it on Google, and read about them. Where does this "information" come from? Does it, an audit report??, come with other supporting information? It's bizarre to merely present four sentences without any context and expect a reply... you *must* have backup information to have this in the first place.

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One of those was actually previously discussed on the LQ forums (I just checked one of them). They offered far more supporting information that this OP did, also.

Looks to me like one of those audit situations where the higher ups call in some security auditor who runs scans of all the servers and submits a report. The higher ups pay good money, don't understand any of it, and then just say, "fix it." Sometimes it actually matters, sometimes it doesn't. The auditors typically dump a lot of information with little context or explanation.

I've taken care of this stuff on Solaris systems using the NSA security guides. The Solaris guide was a collaboration between Sun and the NSA. There are also Windows and Linux guides and application software guides. See http://www.nsa.gov/ia/guidance/secur...es/index.shtml. Select Operating Systems from the left. It shows Red Hat Linux, but much of that should be applicable to other distributions.

When I work through the Solaris guide, I don't necessarily do everything they suggest. Some of it I see as inappropriate to my environment. You're the sysadmin, you choose (unless your boss overrides your choice).

I believe they're actually the results of a QualysGuard PCI scan. Some scans are done in-house while some are done by 3rd parties. Qualys (and most other tools, including such tools as Nessus) actually adds quite a bit research/remediation/mitigation data into their scan results. The OP may be leaving out those details or the auditors may've not given him those details...I don't know. Not all managers are clueless regarding these audits and the steps involved in remediation of scan findings. Sure, they won't know the intimate details, as most may not have worked in a technical field for years, but still, I've seen more than one manager call out either a dumb auditor or a dumb sysadmin.

In my experience, the system owner may not necessarily have a choice in whether or not he/she addresses the findings. I've worked at places that have management backing the scanning process (this is actually essential), but also have seen the system owners play a key part in mitigation or at least justifying why they can't/won't patch a particular system.

Seems so. I googled one and found an amusing blog post of some sysadmin slagging off the test results. Fun.