Anti Spear Phishing
Update 2009-October-11: This package is now hosted at www.scamnailer.com. Please check there for all future information and updates.
Update 2009-June-15: There is now a brand new additional data feed of known phishing email addresses, which I have added to my script.
Spear phishing is a technique used by spammers and scammers to try to get your email username and password. They send you an email claiming to be from your email provider, in which they say that your account will be deleted unless you supply them with your username and password “for authentication” or some other similar ruse.
If they get your username and password, they then use your email account and email provider to send out millions of spam messages. Because the spam comes from a genuine email system (yours!) it will be accepted by most sites and will automatically pass many spam checks.
I have written a script which takes a file of addresses commonly used in these attacks. It also allows an additional list of addressed you can add to. From these, it generates a set of SpamAssassin rules that detect the presence of these addresses, which can be used in MailScanner to stop the spear-phishing attacks completely.
Download the script here. Note that the script is gzipped to ensure your browser doesn’t do anything silly when fetching it, so you’ll need to “gunzip” it before doing anything with it. To start with, just copy it into your “/etc/cron.hourly” directory, and run the command “chmod a+rx /etc/cron.hourly/Spear.Phishing.Rules” to make it run every hour.
It is pretty much a finished script, and is directly usable by you guys without you having to do much to it except read the settings at the top and tweak the filenames if you want to change where it puts things.
I have taken a lot of care to ensure that this won't match any false alarms, I don't just dumbly look for the strings in any surrounding text, which certain commercial AV vendors have been caught doing in the past!
I make a suggestion in the comments at the top of the script about how I use the rule within MailScanner, you probably want to do something similar, and not just delete anything that matches, just in case you do get any false alarms.
It also looks for numbers at the end of the username bit of the address, and assumes that these are numbers which the scammers may change; so if it finds them, it replaces them with a pattern that will match any number instead. There's starting to be a lot of this about, as it's the easiest way for the scammers to try to defeat simple address lists targeted against them, while still being able to remember what addresses they have to check for replies from your dumb users.
I thought I would make it a tiny bit harder for them...
You can also add addresses of your own (which can include "*" as a wildcard character to mean "any series of valid characters" in the email address), one address per line, in an optional extra file. Again, read the top of the script and you'll see it mentioned there. That file is optional, it doesn't matter if it doesn't exist. As a starter, you might want to put
m i c h a e l l o u c a s * @ g m a i l . c o m
(without the extra spaces) in that file, as it will nicely catch a lot of "Job opportunity" spams.
It looks for any of these addresses appearing **anywhere** in the message, not just in the headers. So if you start talking to people about these addresses, don't be surprised when the messages get caught by the trap.
It does a "wget", so make sure you have that binary installed, or else change the script to fetch the file by some other means.
The very end of the script does a "service MailScanner restart", so if you need some other command to restart MailScanner or your SpamAssassin setup, then edit it for your system. It needs to be a "restart" and not a "reload" as I have to force it to re-build the database of SpamAssassin rules. If you don’t use MailScanner, but do use “spamd” in some setup or other, then a simple “service spamd restart” would do at the end of the script.
My aim was that, on a RedHat system running MailScanner, you could just copy the script into /etc/cron.hourly and make it executable, and it will just get on with the job for you. I do advise you read the bit in the script about "SpamAssassin Rule Actions" though.
Please do let me know how you would like me to improve it, and tell me what you think of it in general. (be polite, now!)
Update 13th January 2009:
A colleague on the MailScanner mailing list has made this simpler to use. You don’t have the flexibility of adding your own addresses to the list, but you can get the latest list along with all your regular SpamAssassin updates with the “sa-update” command.
Here are his instructions:
wget http://www.bastionmail.co.uk/spear.txt
sa-update --import spear.txt
Add “spear.bastionmail.com” to the list of channels that you update from (either add “--channel spear.bastionmail.com” to your sa-update command, or add “spear.bastionmail.com” to the file pointed to by the sa-update “--channelfile” command-line option).
Add the key “06EF70A3” to the trusted keys (either add “--gpgkey 06EF70A3” to your sa-update command, or add “06EF70A3” to the file pointed to by the sa-update “--gpgkeyfile” command-line option).
Then these SpamAssassin rules will be automatically updated every time your system runs the “sa-update” command, which is daily on a standard MailScanner system.
Update 2009-June-15: There is now a brand new additional data feed of known phishing email addresses, which I have added to my script.
Spear phishing is a technique used by spammers and scammers to try to get your email username and password. They send you an email claiming to be from your email provider, in which they say that your account will be deleted unless you supply them with your username and password “for authentication” or some other similar ruse.
If they get your username and password, they then use your email account and email provider to send out millions of spam messages. Because the spam comes from a genuine email system (yours!) it will be accepted by most sites and will automatically pass many spam checks.
I have written a script which takes a file of addresses commonly used in these attacks. It also allows an additional list of addressed you can add to. From these, it generates a set of SpamAssassin rules that detect the presence of these addresses, which can be used in MailScanner to stop the spear-phishing attacks completely.
Download the script here. Note that the script is gzipped to ensure your browser doesn’t do anything silly when fetching it, so you’ll need to “gunzip” it before doing anything with it. To start with, just copy it into your “/etc/cron.hourly” directory, and run the command “chmod a+rx /etc/cron.hourly/Spear.Phishing.Rules” to make it run every hour.
It is pretty much a finished script, and is directly usable by you guys without you having to do much to it except read the settings at the top and tweak the filenames if you want to change where it puts things.
I have taken a lot of care to ensure that this won't match any false alarms, I don't just dumbly look for the strings in any surrounding text, which certain commercial AV vendors have been caught doing in the past!
I make a suggestion in the comments at the top of the script about how I use the rule within MailScanner, you probably want to do something similar, and not just delete anything that matches, just in case you do get any false alarms.
It also looks for numbers at the end of the username bit of the address, and assumes that these are numbers which the scammers may change; so if it finds them, it replaces them with a pattern that will match any number instead. There's starting to be a lot of this about, as it's the easiest way for the scammers to try to defeat simple address lists targeted against them, while still being able to remember what addresses they have to check for replies from your dumb users.
I thought I would make it a tiny bit harder for them... You can also add addresses of your own (which can include "*" as a wildcard character to mean "any series of valid characters" in the email address), one address per line, in an optional extra file. Again, read the top of the script and you'll see it mentioned there. That file is optional, it doesn't matter if it doesn't exist. As a starter, you might want to put
m i c h a e l l o u c a s * @ g m a i l . c o m
(without the extra spaces) in that file, as it will nicely catch a lot of "Job opportunity" spams.
It looks for any of these addresses appearing **anywhere** in the message, not just in the headers. So if you start talking to people about these addresses, don't be surprised when the messages get caught by the trap.
It does a "wget", so make sure you have that binary installed, or else change the script to fetch the file by some other means.
The very end of the script does a "service MailScanner restart", so if you need some other command to restart MailScanner or your SpamAssassin setup, then edit it for your system. It needs to be a "restart" and not a "reload" as I have to force it to re-build the database of SpamAssassin rules. If you don’t use MailScanner, but do use “spamd” in some setup or other, then a simple “service spamd restart” would do at the end of the script.
My aim was that, on a RedHat system running MailScanner, you could just copy the script into /etc/cron.hourly and make it executable, and it will just get on with the job for you. I do advise you read the bit in the script about "SpamAssassin Rule Actions" though.
Please do let me know how you would like me to improve it, and tell me what you think of it in general. (be polite, now!)
Update 13th January 2009:
A colleague on the MailScanner mailing list has made this simpler to use. You don’t have the flexibility of adding your own addresses to the list, but you can get the latest list along with all your regular SpamAssassin updates with the “sa-update” command.
Here are his instructions:
wget http://www.bastionmail.co.uk/spear.txt
sa-update --import spear.txt
Add “spear.bastionmail.com” to the list of channels that you update from (either add “--channel spear.bastionmail.com” to your sa-update command, or add “spear.bastionmail.com” to the file pointed to by the sa-update “--channelfile” command-line option).
Add the key “06EF70A3” to the trusted keys (either add “--gpgkey 06EF70A3” to your sa-update command, or add “06EF70A3” to the file pointed to by the sa-update “--gpgkeyfile” command-line option).
Then these SpamAssassin rules will be automatically updated every time your system runs the “sa-update” command, which is daily on a standard MailScanner system.