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Spam Filtering For Small/Medium Business?
or_is_it writes "The company I work for has been growing dramatically and I've been charged with the task of being the gatekeeper for our GFI Spam filters. This involves manually inspecting the subject line/to/from for all caught messages in each filter rule folder. For a company of about 50 people, in one day the number of spam messages can exceed 2,000. Neglect it for a day and you end up with quite a task on your hands. I've made the rules lax enough so important messages can go through, along with a few stray spams, for which I get bitched at. Tighten the rules up and then maybe an important time-sensitive email never gets to its intended recipient, and I get bitched at. Manually reading through all those subject lines is supposed to prevent that, but I'm only human and genuine messages can easily get overlooked. How do larger organizations deal with the spam issue? I can't imagine having one centralized person manually inspecting everyone's junk-mail header is the optimal solution. Purchasing a different commercial mail filter product is a possibility, but I'd like to hear some anecdotal evidence before jumping ship."
I've had to send emails to recipients within the Australian Defence Force (specifically, the Army), and every email sent from a civilian must include a keyword within the subject line. The keyword is to do with whether or not the information is classified or unclassified. Sure, getting all the clients to send all their emails with [companyname] in the subject line is a little annoying, and may not be possible depending on your circumstances, but the chances of spam having that keyword within it is virtually impossible.
Set up an automated filter whereby anything that doesn't have the keyword in the subject gets dumped into a spam box to be sorted later. If the senders do the right thing, it assures their emails will be directed to the correct person.
This is just one example of active spam filtering as opposed to the passive spam filtering used in IT today.
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How do larger organizations deal with the spam issue?
I used to work for a mining company you've heard of. Our department had responsibility for managing the email vendor, who used Spamshark to filter spam coming into the organisation. From my limited knowledge of the setup, Spamshark does basic blacklisting etc. but also does selective blacklisting on specific IPs when an email is flagged by a user. So Alice flags a message as spam, Spamshark figures out the message id, grabs the IP address it came from (it knows because it previously handled the email), and then blacklists that IP for a certain amount of time. Now this internal blacklist is then shared to all the other customers who use Spamshark, so they are now protected too; resulting in a 5 nines hit rate on spam.
Like I said we just handled vendor relations, and the above description might not be totally accurate, but this is what I gathered when we dealt with them. I also remember getting about 10 complaints of spam a month for an organisation with 10's of thousands of email addresses - so it was very effective.
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I can't imagine having one centralized person manually inspecting everyone's junk-mail header is the optimal solution
Actually, that strikes me as a good solution; it's certainly better than having other employees dealing with spam as part of their daily routine and losing 30 minutes/day for everybody in the company. And by centralizing it, you have the ability to pick the tools to make your work more efficient, as opposed to having 50 employees each fiddle with their own spam filters.
This is just a simple guide compiled from my experience:
:)
1. Do what you can on the server. I like to use SpamAssassin to add spam scores to beginning of subject lines, so they sort by score in my inbox (I use "/*_SCORE(0)_*/"). I also automatically delete anything over a score of 11, since the highest I've ever seen a legitimate email score has been "10.something". Realistically, anything above an 8 is the sender's fault and they need to do something about it and anything above an 11 you can safely blame the sender (you won't be the only spam filter deleting their emails).
2. Provide the tools on the client. ThunderBird's "spam marker" is a must, and because it learns from what you mark, you aren't just marking them in vain. Also, to deal with spam in real-time, instead of using the junk folder, I like using the "delete junk!" button from the "Buttons!" add-on. Incoming junk gets marked and marked as read, and after marking the spam the filter missed, I hit "delete junk". Very easy and quick. Pre-configure Thunderbird for everyone.
3. Educate and support. If you have 1 and 2 in place, then make sure everyone knows what you are doing and why you chose to do it. Write a short manual or something. Educate them about their tools. They also need to know NOT to publish their addresses.
The idea is to make spam highly visible, and to make it *quick and easy* to deal with. Knowing you've facilitated these two goals should be enough to impress your employer and earn the respect you deserve from everyone you serve
I spent a few days migrating 100,000 emails from Windows Mail, because it was horrible. Thunderbird is a godsend and the add-ons make all the difference. If there is something you dislike or want, chances are someone made an add-on for it.
btw 2000 messages is *not* a lot of spam. It will get far worse with time.
Businesses shouldn't be using those for internal communications anyway. Set up a jabber or irc server internally for that.
Gah they are so expensive. And to keep them up to date is ridiculously expensive. I prefer free with ASSP.
Additionally I have a serious problem with the backscatter they cause. They should reject mail at SMTP time and not bounce them.
But Barracuda support is very very good. Very responsive and timely and overall a good people orgaization which can make the difference for wanting to deal with them.
Chuck
Consider as well that the Barracuda appliances consist of (a) an open-source operating system (b) an open-source MTA (c) an open-source web server (d) an open-source spam scanner (e) an open-source virus scanner (f) other pieces of open-source software and (g) use community-mintained DNSBLs and RHSBLs. This is all held together with proprietary (closed-source) code, mostly for the purpose of providing a poorly-designed GUI interface. Any competent email system administrator should be able to create their own near-equivalent in an afternoon; it's not difficult. Such homebrewed creations have repeatedly been shown to vastly outperform Barracudas on multiple metrics, including cost, scalability, customization, security, and perhaps most importantly -- adaptability to new spammer techniques. (Barracuda is years behind the times and falling further back.)
It's very tempting to "just buy an appliance" and consider the problem solved, but it doesn't work. There's no substitute for expertise -- and given that much of that expertise is available for free, for the asking, on lists such as spam-l and spamtools and so on, it's difficult to understand why anyone would choose not to avail themselves of it.
Pardon me, but I just don't see the "size". I personally (and professionally) receive well over 3'000 spam e-mails each and every day. I take about three to five minutes to run through them. For 6'000 in two days, I take four to seven minutes.
." which get selected and deleted in a block of one hundred at a time.
I do it without a spam filter of any kind. I have only two technique.
First, simple rule-based filters throw clients and friends into their own folders by from: line alone. That covers everyone I know in advance.
The second set of rules simply looks for my full name, my company name, my e-mail signature, my telephone number, or my mailing address. These into the "it's damn likely a legitimate e-mail" folder. This folder gets about 2 spam e-mails per week.
The remaining I simply run through, in outlook express of all clients. Sorting wins the day. The greatest trick? Sort by the to: field. It doesn't take long to see that 75 messages went to moocow@mydomain.com, 75sevens@mydomain.com, or some other horribly malformed address to that doesn't exist. Sorting by subject does similar things -- like give you "70% off . .
Your spam has very simple patterns to look for. Sort by them, click the first, shift-click the last, and hit delete.
Last year, I was contracted by Viagra's H.R. department to do some quick work, I made it through unscathed.
I've seen Postini-filtered mailboxes. Don't bother.
Only solution that I know works is my own: Postfix with amavisd-new, spamassassin, clamav, postgrey, along with FuzzyOCR on smaller installs, though setting that up on a separate system to filter through might cover a large organization. Don't forget to include things like Spamhaus' Zen list, any of the *.countries.dk.net blocklists to filter out any geographical areas from which you don't expect legitimate mail, and also helo filtering--if the connecting mail server can't say helo/ehlo with something that resolves in DNS, it can just bugger right off.
Tell your boss that expecting not to lose email with spam filters in place is unreasonable, and that tasking one human to eyeball all the rejects is a serious misapplication of time and money.
Best of all, you should educate your boss to realize that email is not a reliable messaging system. There are far too many points of failure that could cause a message to be lost, most of them being outside of your own or your company's control. There exist many better ways to send time-sensitive material, like fax, overnight mail, and telephone calls. If a severe amount of money is to be lost because an email didn't make it on time or made it not at all, then the message should have been sent over a more reliable medium in addition to being emailed.
Only the severely clueless would rely on a system like the one you have set up. You have to allow for a certain failure rate in any system. That's a basic principle of quality control methods that have been in use for decades.