Tag Archives: security

How to Test Your SPAM Filter

Does my Email Filtering Solution Work?

Sometimes as email administrators we need to test if the SPAM filter works and is filtering messages. In order to do this we need to send a test message with content that we are sure is rated as SPAM.

GTUBE – Generic Test for Unsolicited Bulk Email

The GTUBE the “Generic Test for Unsolicited Bulk Email” is a test that can verify if your antispam filter is installed correctly and is detecting incoming spam.
GTUBE works in a similar fashion to the EICAR anti-virus test file.
Insert the following string in any email message and your antispam filter should detect it and filter it accordingly.
XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X
Note that this string should be written in one line, without whitespace or line breaks.
Note that this string and can be reproduced freely, without attribution; they are hereby placed in the public domain.

Public Email Addresses Cause a Lot of Spam

The Inter-Department debate

Within most of the companies there are two views about how the technology should be used.
Marketing is always looking for ways to attract people to get potential customers involved in Companies’ activities. Sometimes they would do anything to make the Web site visitors rise, even if this doesn’t translate into sales. There is a little desperation in their actions. Many times this translates into SPAM, and exposure to other attacks.
On the other hand the IT infrastructure will always try to secure as much as possible forgetting that tightening up too much will make the customer go away.
It takes a good collaboration between the Marketing and the IT department to insure the best balance between a secure IT environment and the maximum interaction with your potential clients.
It also takes well trained personnel and the training need to be interdisciplinary. For instance Marketing need Technology knowledge and IT need Marketing knowledge.
Following I will present some of the frequent mistakes I encountered in my experience as an IT administrator. I will underline the misconception behind some of these mistakes and show what can be done to correct them.

Common Mistakes when Publishing Email Contacts and How to fix the Mistakes

A common mistake of Marketing is to publish email addresses on Internet. The misconception is that people are not comfortable to use forms and they will run away from a contact form because it involves more effort in order to contact someone within the company.
This is a partial true. This depends on the way your company makes business and on the product you sell. If you sell an inexpensive product and the main goal is to expedite the process then make a contact address public could be a way. This is the easiest and the most convenient way of making yourself available, (after phone). If you sell an expensive product/service, a contact address for support then you should go with Web Contact Forms.
Using a Web Contact Form is the most secure and easy way to maintain email communication. You can publish the link of this form on any website, Social Networking site, or Web profile.
If you are not using Web-forms the amount of SPAM once you publish your email address on Internet is exponential; once your email gets discovered by spider bots is going to be used more and more.
Your contact email address doesn’t have to be published on Internet.   Whoever is looking to get in contact with your company will take the time to fill in a form and a CAPTCHA field. Or they can call; you should publish your phone numbers on the Web.
Or even better setup a chat page on your website and have an option so that you client can request a phone call. Most of the times a company will get better deals for Long Distance calls than a consumer.
On the Social Media profiles use contact forms and links to your website’s contact form instead of publishing an email address.
Social Media pages are very popular and they are crawled more often than other content types. Any email address published will be discovered very quickly by spider-bots.
If your business cannot function without a published email address you can take a few measures to minimize the impact on your system:
Publish an image of your email address and not the email address html coded. This will prevent bots to discover your email addresses while providing users a public email address.
If this is still not acceptable and you want the email address to be a clickable email link, be prepared to change the public email address on a regular basis.
When you change a public email address, set up automatic reply on the old ones and keep the account active for a while. The automatic reply message should point to the newest email address.
Automatic SPAM software will not know that the email has changed and a legitimate sender will get the reply with the newest email address.
The automatic reply should also mention the website page that contains the newest contact information. (Let’s say you changed three email addresses within a week, a client who added you in their Address Book a week ago will have to send three emails to reach you.
The email addresses should be rather complex than intuitive, see this article for explanations:Preventing Domain Name Spam.
Create and maintain a list with all of the Web Pages and Social media sites accounts that use the public email address. This way you won’t forget to make the change everywhere when you need to update the contact info.
Use personal Antispam filters such as: Mailwasher, (free and Pro versions), ChoiceMail One, Spam Killer, CA Anti-Spam, SpamNet, Spam Agent, SPAMfighter, Spam Buster, iHateSpam, SpamBully, Intego Personal Antispam X5, etc…
Another common mistake is to mix up personal communication with business communication.
The reasoning behind this is that: “I am going to give the address only to friends so it’s safe”. Nothing more wrong, there is always one of your friends that will get hacked, personal computers are more prone to be infected and your address will get used and distributed to SPAM lists. See here a more detailed explanation: Ho to prevent Spam.
Never use your business email address for personal stuff. It will end up spammed. Do not use it to exchange email messages with friends, to subscribe to online services etc…
Do not use a personal business email address to create online accounts even if they are business related. Use generic accounts that you afford to change at any time.

Information For System Administrators

Implement SPF – see this article.
Train your users and implement written policies about the email usage within the company.
Use different domain names for web presence and for daily correspondence.
If you are a system administrator you can look at various corporate targeted solutions to reduce spam.
Corporate Level Antispam Solutions
Server Based Antispam Software, Antispam Appliances (Gateway based Anti-Spam), Hosted antispam filtering.
A few solutions no necessarily the best: are Google Postini, Barracuda Networks, MailFoundry, IronPort, Spamassassin, SPAMD (BSD), Trend Micro, GFI MailEssentials, MailMarshal, Symantec Brightmail, and Roaring Penguins’ CanIt Pro.
More Antispam solutions here: Comercial Antispam Solutions

Remember is always better to prevent than to fix.

Corporate Antispam Solutions

Linux Mail Servers or other SMTP servers

Hexamail Guard
Kaspersky Anti-Spam Enterprise Edition
Declude MailProtector
Ruckus MailFILTER
Vorras Classifier
GWAVA for Novell GroupWise
Trend Micro

Exchange

MailSite MP Email Gateway Software
Symantec Premium AntiSpam
Hexamail Guard
MailFender for Exchange Server
iQ.Suite
Pro Exchange Spam Smacker
XWall
modusGate™ MS Exchange Anti-Spam Gateway
GWAVA for Microsoft Exchange
Trend Micro

Windows

BCware NoSpam
Pinjo
DynaComm i:mail
MAILsweeper Business Suite
SpamBolt
Surf Control
AlliGate
Spam Sleuth Enterprise
NetIQ MailMarshal
Visnetic MailScan
Omniquad Mailwall
Lightspeed Total Traffic Control
SMTPTrap
Philter
Fluffy the SMTPGuardDog
Catch!
IDRSMTPProxy
Spam Manager Professional
MailMax
eTrust Secure Content Manager
Leon
mxORB
GWGuardian
Rockliffe MailSite MP
ADVmserve

Gateway (Appliance or Installable Software)

Astaro Security Gateway
Alligate (Windows)
IMGate (FreeBSD 7)
Symantec Brightmail Gateway
iQ.Suite (Windows \ ISA)
Axway MailGate (Linux)
XWall
Active SMTP
ModusGate Antispam Appliance
MXtreme
Cloudmark Authority
SpamTitan
MailFoundry
iForce Mail Firewall
Barracuda Networks
Roaring Penguin CanIt Appliance
SpamKiller 3000 series Appliances
Watchguard Spamscreen
Arska Mailwall
Bizanga

Domino

M-Switch Anti-Spam
Symantec Premium AntiSpam (Exchange and Domino)
SpamSentinel
MIMEShield    

Service (Third party Hosted MX) – Subscription Based

SpamSentinel
MailSite MP Email Gateway Software
Declude MailProtector
Postini (Now a Google service)
Mxpolice
SPAMfighter
MXGuarddog
CudaMail
Remote Anti Spam
GFI MAX MailProtection

Email address Spoofing – Someone is Using My address to Send Spam

Someone is Using Your Address to Send SPAM

You just got a bounce-back email saying that your email didn’t reach the destination because the recipient doesn’t exist. Nothing unusual, this is something that happens to anybody who is using email regularly; except you didn’t send that email. How could this happen? If you are an email server administrator and many of your users get this kind of bounce-back they all start to complain at once, thinking that your server has been hijacked. What can you do to stop this, and how to reassure your users that you haven’t been hijacked?

Sender Address Forgery known as email address spoofing is not a new technique. It is used for many things from spamming organizations to sending viruses and supporting scamming schemes where the sender fakes his identity.

Effective ways to stop Spammers to Use Your Domain Name

Publish SPF Data
SPF (Sender Policy Framework) is a method that allows you to publish which mail servers are authorized to send email for your domain. SPF uses a DNS record that tells email servers which servers are the servers that are trusted sources of email for the specific domain and how much to trust other sources of email originating from that domain. Destination servers might have the SPF checking implemented or not. Many of the today’s servers are SPF checking enabled.
Destination servers check this record and act in consequence. Anti-spam software on servers receiving emails, score an email based on SPF record and other criteria and accept or reject the email based on the total score. For instance if the SPF record tells that any emails originating from non authorized servers should not be trusted the email gets the necessary points to be treated as SPAM and it gets rejected. If the SPF record treats the non authorized servers neutral the message could pass or could be rejected if other it contains other SPAM characteristics.
Do not publish any email addresses on Web pages. This is the most common place for spammers to get valid email addresses and use them to forge email messages

If your company runs its own mail server configure it to ignore email sent to non-existent addresses in your domain. If your server sends a non-delivery report you reveal to a spammer valid addresses in your domain (the ones that don’t send NDRs). This attracts spam to those addresses. You waste bandwidth. The most common reason to send NDR’s for non-existent addresses is to let people know that they misspelled the address. Miss-addressed email can get lost easier.

If your domain gets blacklisted because of spoofing you have to contact the list which blacklisted you and show the Administrator what you did to correct the problem. This is very unlikely since the sender usually spoofs only the email sender and not the server’s address. A blacklist Admin should be able to figure out this.

Preventing Domain Name Spam

What is domain name spam?
Domain Name Spam is a spamming technique where the sender only knows the domain name and he doesn’t have any valid email address in the domain. The technique involves sending emails to all the possible combinations or to a nicely crafted dictionary. The most common addresses in such a dictionary are:
• info@
• mail@
• sales@
• contact@
• contacts@
• root@
• help@
• home@
• contactus@
• enquiries@
• webmaster@
• hr
• shipping
The generic list is actually very long but I won’t include here all of the addresses.
Other possible entries in the dictionary are common names and different combination of these names. Let’s take for instance the name John Doe. A few possible combinations and the most used are: john.doe@company.com, j.doe@company.com, john.d@company.com, johndoe@company.com, etc…
What can you do to discourage and stop this kind of spam?
Set up your email server so it will not accept too many emails from the same server within a specified time frame.
Do not send NDR for unknown recipients, this will inform the attacker about the invalidity of those addresses, this is good information for a spammer. The disadvantage with this is that misspells of an address from a legitimate sender will not inform them about the error.

Use less commonly used prefixes for your email addresses.
Instead of “info@yoursite.com” use “askaquestion@yoursite.com”.
Instead of “webmaster@yoursite.com” use “yourname@yoursite.com”.
Instead of “help@yoursite.com” use “problem@yoursite.com”.
You do want to still keep your email addresses professional and to make sense to your customers. An email address like Egfa13wge2@yoursite.com will fool domain name spammers, but customers will be tempted to delete the email when they see such an email address in the “To” field of their email.
Also, don’t forget that many domain name spammers hope you have your catch-all turned on. This means that even sending an email to “any-address@yoursite.com” will end up in the admin’s mailbox even if that email address doesn’t exist. Unless you have a need for your catch-all to be turned on, you should have it turned off by default.