Problem s viry na SMTP

[Petr Vyhnal]

Pokud to dobre chapu, tak timto ale zakazete pristup na veskere vnejsi 
SMTP a uzivatele dostanou timeout chybu. Mozna ze lepsi zpusob bude 
pouzit REDIRECT, ktery prevezme paket posilany na externi SMTP a doruci 
jej lokalnimu SMTP. Viz.:


      REDIRECT

This target is only valid in the *nat* table, in the *PREROUTING* and 
*OUTPUT* chains, and user-defined chains which are only called from 
those chains. It alters the destination IP address to send the packet to 
the machine itself (locally-generated packets are mapped to the 
127.0.0.1 address). It takes one option:

*--to-ports* /port/[-/port/]
    This specifies a destination port or range of ports to use: without
    this, the destination port is never altered. This is only valid if
    the rule also specifies *-p tcp* or *-p udp*. 

>  /sbin/iptables -t nat -A PREROUTING -p tcp --dport 25 -j DROP
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