Linux spam firewall

The hidden dangers of spam: spam has gone from virtually nothing four years ago to a major problem today. It is now estimated that spam accounts for about

To date most articles written have looked at spam from the receiving end, but there are hidden dangers to all legitimate companies at the 'sending end' of spam. So what are they, and what is meant when we talk of the sending end of spam?

One sending end spam issue is the highjacking and illegal use of a legitimate company's Internet domain (e.g. mycompany.co.uk). This manifests itself in the 'From' address of a spam message, which can--and generally is spoofed using a domain that does not lead back to the spammer. Generally the 'user' is randomly generated, so the same spam message will appear to come from multiple people.

This can lead to the domain being blacklisted within the Internet--potentially stopping the bulk of legitimate emails from the company being delivered and there is a reputation risk as well.

Another 'sending' type problem is where a system or PC, that is permanently connected to the Internet via some broadband type connection, is highjacked to send spam. The problem for the person or company owning the highjacked system or PC is that the Internet Service Provider could withdraw service. Sending spam is against most, if not all, UK IPS's acceptable use policies. Whether Internet service is withdrawn temporarily, until the system of PC is fixed, or permanently, will be down to the ISP involved and mitigating circumstances (e.g. how quickly did you take your system or PC offline, has the problem happened before etc).

Loosing Internet connectivity, even for a short period of time, can impact a business, and there could be costs involved in getting your systems of PC up to a standard required by the ISP before service gets reinstated.

So spam is more than an annoying clogging of your company email 'inboxes', it could have a much bigger impact on your business than you imagined. There is little to nothing you can do to stop your Internet domain being highjacked; but you should remain vigilant against it happening. For instance, do you regularly check your email system's postmaster account for 'bounced' messages. A lot of bounced messages that clearly were not generated by your company is an indication something is wrong, and needs investigating.

Are your systems or PCs behind a firewall? Is the firewall properly set up, and when was the last time you had an independent assessment of your Internet security; six months, a year ago of never? Are your systems or PC running 'out of the box' or have they been hardened against hacking and are they up to date with security patches?

Remember that it is not just Microsoft, but Linux and Unix as well. Typically a day does not pass without there being at least one, and often three or more system security vulnerability announcements and of ten one of them will be for Linux.

Keeping your systems in good, secure order, is a matter of good IT governance; which forms part of good corporate governance. You would not dream of leaving your premises open when everyone had gone home, and you probably have fitted strong quality locks to the doors and keep your valuables in a safe. It is part of the cost of doing business, so why is IT any different? Given the high dependence on networks (the telephone, the Internet and the office LAN) isn't it time you woke up to these hidden dangers. Security (of IT systems) is not a bolt on, it is a culture. You do it (and well) without thinking.