The TCP Wrappers are a set of programs and libraries used to add some extra security checks and logging functionality to service daemons. When a request comes in for a service tcpd checks the incoming request and compares it with rules in the files /etc/hosts.allow and /etc/hosts.deny. At the simplest level tcpd can allow or deny the request and log the access.
The tcp wappers are available from:
ftp://ftp.porcupine.org/pub/security/index.html
A typical hosts.deny file:
ALL : ALL
A hosts.allow file entry:
vsftpd: 129.19.
A tcp wrapper log file entry:
Sep 14 08:51:32 pipeline.adams.edu vsftpd[29560]: refused connect from 211.22.59.242