Chapter 33 Anti-Spam

Figure 421 DNSBL Example

 

 

 

 

DNSBL 1

1

2

 

Not spam.

 

 

IPs: a.b.c.d

 

 

 

 

w.x.y.z

 

 

 

DNSBL 2

4

3

 

 

 

Spam!

 

 

 

 

DNSBL 3

1The ZyWALL checks the e-mail’s header for sender or relay IP addresses and sends them to all of the DNSBL domains configured in the ZyWALL.

2The DNSBL servers reply as to whether or not the IP addresses match an entry in their list. In this example, DNSBL 1’s reply came first. Since DNSBL 1 says the IP addresses are not in its list, the ZyWALL waits for more responses.

3DNSBL 2 has one of the IP addresses in its list.

4The ZyWALL immediately classifies the e-mail as spam and takes the action for spam that you defined in the anti-spam policy (in this example it was an SMTP mail and the defined action is to drop the mail). After a positive match is found in a DNSBL, the ZyWALL does not wait for any more DNSBL responses.

33.2Before You Begin

Configure your zones before you configure anti-spam.

33.3 The Anti-Spam General Screen

Click Anti-X> Anti-Spamto open the Anti-Spam General screen. Use this screen to turn the anti-spam feature on or off and manage anti-spam policies. You can also select the action the ZyWALL takes when the mail sessions threshold is reached.

 

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ZyWALL USG 100/200 Series User’s Guide