Installing and configuring the nscd daemon can greatly improve the performance of any activity that requires host lookups. Examples would be web browsing, ftping, wgeting, etc.

Tools you will need:

1. nscd
2. keyboard
3. device or fingers to clickey click the keyboard
4. file editing skills

Instructions:

1. install nscd
2. configure nscd.conf
3. start nscd
4. set nscd to start at boot

By default /etc/nscd.conf contains:
enable-cache. . hosts. . no
Change it to:
enable-cache. . hosts. . yes

The positive ttl and negative ttl are displayed in seconds. Set them to a reasonable value. Mine are positive = 86400 and negative = 20.

Important! If you are running a service that relies on forward/reverse lookup checks, don't do this! An example would be, if you are running an smtp server which only accepts email from a host with a valid ptr record.

Average home users should see a significant increase in performance because we are reducing the number of lookups your machine has to perform.

[quote author=Thing link=board=2;threadid=5170;start=0#msg43112 date=1076254498]
Important! If you are running a service that relies on forward/reverse lookup checks, don't do this! An example would be, if you are running an smtp server which only accepts email from a host with a valid ptr record.
[/quote]

Why not?

Quote from Security Focus:

[quote] The Name Service Cache Daemon (nscd) has a default behavior that
does not allow applications to validate DNS "PTR" records against
"A" records.

In particular, nscd caches a request for a "PTR" record, and when a
request comes later for the "A" record, nscd simply divulges the
information from the cached "PTR" record, instead of querying the
authoritative DNS for the "A" record.[/quote]

As far as I know, this is still the case. It is terribly unimportant for an average home user.

[quote author=Thing link=board=2;threadid=5170;start=0#msg43118 date=1076255470]
As far as I know, this is still the case. It is terribly unimportant for an average home user.
[/quote]

I'd say that could be terribly important for a home user... What are the ways to force someone to do a ptr lookup? Access something that generates a log entry on his machine?

If you can fool the home user into doing a ptr lookup for your IP, and return www.citibank.com, then you can do a perfect hijack of that site?

Netscape, Konqueror, Opera and Mozilla all have their own built in resolvers. They utilize the DNS resolver libraries but don't query the nscd db.

[quote author=Thing link=board=2;threadid=5170;start=0#msg43296 date=1076336190]
Netscape, Konqueror, Opera and Mozilla all have their own built in resolvers. They utilize the DNS resolver libraries but don't query the nscd db.
[/quote]

Hmm, so that must reduce the usefulness of nscd.. What does query it? Telnet/b.net/irc etc?