Hi,
I am a noob.I ran nmap and saw SMUX running at port no 199,which was not there before.Any help regarding what that is and how to stop that would be much appreciated.

SNMP -- Simple Network Management Protocol. aka 'Security Not My Problem'

SMUX -- SNMP Unix Multiplexer

I suggest you turn off or remove snmpd unless you know what it is and are sure you need it


service snmpd stop
chkconfig snmpd off

To turn off SMUX when you don't have the options of recompiling from source
to disable SMUX support, you have to give it an invalid IP address to bind
to. This may be OS specific. On Linux, if I put this in my snmpd.conf:

smuxsocket 1.0.0.0

I get an error at startup, and lsof or netstat show that snmpd is no longer
listenting on port 199. If you get and error message about the smuxsocket
token not being recognized, then you're out of luck. You'll have to recompile
from source (or just use local firewall rules to block connections to port
199).

If you don't want to disable snmpd, it's possible to make firewall rule to block only the incoming packets on that port - 199 (SMUX)
e.g the Packet Filter:

>_ block in on eth0 proto { tcp, udp } from any to any port 199