Linux control remote access to SSHD

Test environment: Linux centos6.5

1. hosts.allow File configuration:

Modify the/etc/hosts.allow file
#
# Hosts.allow This file describes the names of the hosts which is
# allowed to use the local INET services, as decided
# by the '/USR/SBIN/TCPD ' server.
#
Sshd:210.13.218.*:allow
Sshd:222.77.15.*:allow
The above notation means that 210 and 2,222 IP segments are allowed to connect to the SSHD service (which must be used in conjunction with the Hosts.deny file), and of course "allow" can be omitted entirely. Of course, if the administrator is in one IP, then this is easier to write.
all:218.24.129.110//He accepts all requests for 110 of this IP!

2. hosts.deny file Configuration
/etc/hosts.deny file, this file is a list of denial of service, the file content is as follows:
#
# Hosts.deny This file describes the names of the hosts which is
# *not* allowed to use the local INET services, as decided
# by the '/USR/SBIN/TCPD ' server.
#
# The Portmap line was redundant, but it was left to remind
# The new secure Portmap uses Hosts.deny and Hosts.allow. In particular
# should know that NFS uses portmap!
Sshd:all:deny
Note: Sshd:all:deny indicates that all sshd remote connections have been rejected. :d Eny can be omitted.
So: When the Hosts.allow and Host.deny conflict, the Hosts.allow settings prevail.

Effective immediately upon completion of the modification.

3. Extension:
1. Disable SSH functionality for all IP access to Linux
You can add a row in/etc/hosts.deny Sshd:all:deny

2. Disable an IP (192.168.11.112) Access SSH feature
You can add a row in/etc/hosts.deny sshd:192.168.11.112

3. If there are sshd:192.168.11.112 rules at/etc/hosts.deny and/etc/hosts.allow, then 192.168.11.112 can access the host's SSH service

Summary: This method can control some non-authorized access, but not once and for all! When we look at the service log, we may see a lot of scan records, not or directly for the root user, then control your access list is very useful!

Linux control remote access to SSHD