what is hardening a server?

Answer 1

Basically it is a process of disabling services that are not required for normal operation in your environment in an attempt to minimize attack/exploits on the system. I've included a general explanation below from Wikipedia.

Answer 2

"Hardening involves removing any services that don't contribute to the function of the server, reducing the number of possible vulnerabilities available to the would-be hacker."
http://msevents.microsoft.com/cui/WebCastEventDetails.aspx?EventID=1032280301&EventCategory=5&culture=en-US&CountryCode=US

"Hardened Security
Hardening is about minimizing risk and increasing robustness. Hardening a server or workstation that is directly Internet accessible includes the following:

Reducing the number of network services that are running and accessible to the Internet.

Removing unnecessary software and features, which reduces the overall complexity of the system. This includes removing additional protocols such as IPX, AppleTalk, NetBIOS, DLC, LAT, and DecNET.

Removing software that allows access to internal system information, such as SNMP.

Removing insecure remote control software, such as X Window or the ADMIN$ share for remote Windows NT administration.

Applying all known security updates and service packs. Often times security exploits in necessary software such as DNS are resolved in a simple configuration change or security patch.

Enabling traffic filters if available. Windows NT and most UNIX systems have built-in or freely available software that allows more control of the kinds and sources of IP traffic that are accepted.

Removing unnecessary accounts on the system. Rename existing administrative or root accounts to something unique and hard to guess.

Removing unnecessary and overly generous file permissions for both accounts and the file system."
http://www.informit.com/articles/article.asp?p=130856&seqNum=8&rl=1

Answer 3

Hardening a server refers to the process of making a server more secure.

Some steps (far from all!) that are part of hardening a server:
- turning off unneeded services
- enabling and configuring a firewall
- tightening filesystem permissions
- configuring the needed services in a secure way