| Providing security against email related threats has | | | | authentication-based relay is available, setup and |
| become a burden for most IT professionals in 2006. | | | | configure it too. NOTE: If the relay is not set |
| According to a recent study by Postini, spam and | | | | properly, spammers will be able to send email from |
| email viruses now make up to 80% of all emails sent | | | | your mail server. This exploit is commonly known as |
| out as compared to 50% in 2000. As a result, IT | | | | an "Open Relay" or a "Spam Relay." Use the Open |
| professionals now face a tougher challenge in | | | | Relay test at to check if spammers can relay mail |
| providing network security for this amount of spam. | | | | from your server. |
| IT professionals also have the disadvantage of | | | | 5. |
| defending against new forms of email threats such | | | | Black Lists: Setup your mail server(s) with a black list. |
| as spam zombies, directory harvest attacks, mass | | | | A black list (black hole list) is a database or listing of |
| mailing trojans, as well as the latest email virus. | | | | known spam sources. Most modern email servers can |
| In this article, I have listed the seven most effective | | | | be configured to query inbound email against online |
| spam fighting tips for organizations with in-house mail | | | | blacklists. Messages originating from these sources |
| servers. These seven tips are proven techniques I | | | | can then be blocked. I recommend configuring your |
| have used for my customers, partners and | | | | email server with SpamHaus blacklist. Spamhaus.org is |
| associates who wish to tighten their perimeter | | | | an excellent free service to use. Some other good |
| (network) security. | | | | blacklists are DBSL and SpamCop. |
| 1. | | | | 6. |
| Firewall: A firewall is your first line of defense against | | | | Reverse DNS: Reverse DNS (rDNS) associates an IP |
| hackers, crackers, and spammers. Without a firewall, | | | | Address with a Domain Name. Most mail servers, as |
| your network is a disaster waiting to happen and | | | | an anti-spam feature, often use a reverse DNS |
| could give any novice hacker free reign over your | | | | lookup to compare an email address domain name |
| network. If your organization has multiple Internet | | | | with its IP address. If the IP address found from the |
| users, this tool is essential for securing your network. | | | | rDNS lookup does not match the domain name, it is |
| 2. | | | | probably spam. If you haven't done so, setup and |
| Block Port 25: On your firewall, allow outbound traffic | | | | configure reverse DNS records on your DNS server. |
| on TCP port 25 for all mail servers. Block traffic on | | | | 7. |
| outbound TCP port 25 for all other computers and | | | | Anti-Virus Scan: There are many tools that provide |
| servers. On the Internet, TCP port 25 is used for | | | | adequate anti-virus protection for desktops at the |
| email traffic through SMTP (Simple Mail Transport | | | | workplace. Most anti-virus software is good at |
| Protocol). Blocking this port is a good security | | | | detecting viral threats that proliferate email spam |
| practice and prevents mass mailing worms and spam | | | | such as mass mailing worms, trojans, and directory |
| zombies from sending mail from your users' | | | | harvesters. Large organizations might want to use |
| computers. | | | | enterprise anti-spam software with management and |
| 3. | | | | monitoring tools that will allow tracking of network |
| Managed Email Filtering: Consider using a managed | | | | virus outbreaks. |
| filtering solution such as Postini, Brightmail, or | | | | Recommended Links: - [Postini service - managed |
| SpamSoap. Managed Email Filtering services quarantine | | | | filtering, 1 to 500 users] - [Postini service - managed |
| spam, viruses, and email threats before reaching the | | | | filtering, 500+ users] - [Blacklist] - [Blacklist] - [Blacklist] |
| email servers on your network. In comparison to | | | | - [Open relay test] - [DNS report/open relay test] - |
| desktop filters and server appliances, managed | | | | [Spam database lookup and open relay test] - [Spam |
| filtering services provide superior perimeter (network) | | | | Zombie Article] |
| protection by preventing delivery of spam and | | | | Email viruses and related threats delivered through |
| viruses to your network and servers. | | | | spam have cost businesses billions of dollars in |
| 4. | | | | expenses and lost productivity. Each spam email sent |
| Check Relay Setting: A mail server's relay setting | | | | or received from your domain costs your |
| controls which computers and servers are able to | | | | organization money and bandwidth. By implementing |
| send SMTP email on your organization's behalf. Check | | | | these seven tips, your organization can reduce spam |
| your settings and limit the IP address range to email | | | | and recover costs. |
| users on your local network. Some mail servers have | | | | This article: © Copyright 2006 Todd Green and free |
| settings to limit email relay through authentication. If | | | | for republishing. |