/isbg

IMAP Spam Begone (isbg): a script that makes it easy to scan an IMAP inbox for spam using SpamAssassin and get your spam moved to another folder.

Primary LanguagePythonOtherNOASSERTION

IMAP Spam Begone

isbg is a script that makes it easy to scan an IMAP inbox for spam using SpamAssassin and get your spam moved to another folder.

Unlike the normal mode of deployments for SpamAssassin, isbg does not need to be involved in mail delivery, and can run on completely different machines to where your mailbox actually is. So this is the perfect tool to take good care of your ISP mailbox without having to leave it.

Features

  • Works with all common IMAP servers
  • Works on Linux, MacOS X and Windows (even smartphones!)
  • Can do IMAP over SSL
  • Can remember your password
  • Will work painlessly against multiple IMAP accounts and servers
  • Is not involved in the mail delivery process, and so can run on any machine that can contact your IMAP server
  • Highly configurable
  • Sensible defaults so you don't have to do any configuring :-)
  • Compatibility with Python 2.4, 2.5, 2.6
  • Possibility to skip spam detection to stick only to the teach feature
  • Don't fail when meeting horrible and bad formed mail
  • Lock file to prevent multiple instance to run at the same time (for cron jobs)

New in 0.99

  • Drastic performance enhancement (up to 1000x speeder!)
  • Lock file to prevent multiple instance to run at the same time (for cron jobs)
  • SSL fixed
  • Don't fail when meeting horrible and bad formed mail
  • Remember mails teached as Spam and Ham
  • Automatically delete mail with very high spam score

Does it work?

Yes, very well. It has been filtering my work email, some of which comes from a legacy email address that is from a spam unfiltered system. I run it as a cronjob every 15 minutes, and have had it doing that for 6 months. I get about 500 spams a month. Many other users have been using it for a variety of servers from a variety of platforms. There are no known outstanding bugs.

Installation

Install from source

Make sure you have SpamAssassin installed. All the necessary information can be found on the SpamAssassin wiki.

SpamAssassin should be on your $PATH (it installs in /usr/bin/ by default)

Download isbg.py. You can rename it to anything you want, and make it executable (chmod 555 isbg.py). It is written in the Python scripting language. Python is installed by default on most Linux systems. You can can find out more about Python at www.python.org

Simply invoke it by whatever name you called the file. For a better experience, you can add a bash alias to your ~/.bashrc file. Here alias isbg="/path/to/isbg.py" should do the trick.

Install in Debian

There is a package in mentor.debian.net pending approval from the community. There should thus be a packaged version soon.

Your first run

SpamAssassin

If you have never used SpamAssassin before, you'll probably be quite nervous about it being too good and taking out legitimate email, or not taking out enough spam. It has an easily adustable threshold to change how aggressive it is. Run the following command to create your preferences file.

$ spamassassin  </dev/null >/dev/null
Created user preferences file: /home/rogerb/.spamassassin/user_prefs

You can then edit $HOME/.spamassassin/user_prefs and change the thresholds.

You can also edit the system-wide settings in /etc/spamassassin/locals.cf.

If you want to use the --learnspambox or --learnhambox, you'll have to configure your spamassassin.

Configure your spamassassin

If you want to use --learnspambox or --learnhambox features, you have to add this configuration:

Allow Tell

You have to start spamd with the --allow-tell option.

On Debian systems (Debian and Ubuntu), you have to edit /etc/default/spamassassin and replace:

OPTIONS="-D --create-prefs --max-children 5 --helper-home-dir"

by:

OPTIONS="-D --allow-tell --create-prefs --max-children 5 --helper-home-dir"

Don't forget to restart your spamd server after that (sudo service spamassassin restart on Debian).

CLI Options

The default behaviour of isbg is to not make any changes your Inbox unless you specify specific command line options. Consequently you can experiment without worry at the begining.

Your first step is to create a new folder to receive suspected spam. I use one named 'spam'.

Run isbg with the --help option to see what options are available:

Usage:
    isbg.py [options]
    isbg.py (-h | --help)
    isbg.py --version

Options:
    --delete             The spams will be marked for deletion from your inbox
    --deletehigherthan # Delete any spam with a score higher than #
    --exitcodes          Use exitcodes to detail  what happened
    --expunge            Cause marked for deletion messages to also be deleted
                         (only useful if --delete is specified)
    --flag               The spams will be flagged in your inbox
    --gmail              Delete by copying to '[Gmail]/Trash' folder 
    --help               Show the help screen
    --ignorelockfile     Don't stop if lock file is present
    --imaphost hostname  IMAP server name
    --imaplist           List imap directories
    --imappasswd passwd  IMAP account password
    --imapport port      Use a custom port
    --imapuser username  Who you login as
    --imapinbox mbox     Name of your inbox folder
    --learnspambox mbox  Name of your learn spam folder
    --learnhambox mbox   Name of your learn ham folder
    --learnthendestroy   Mark learnt messages for deletion
    --lockfilegrace #    Set the lifetime of the lock file to # (in minutes)
    --lockfilename file  Override the lock file name
    --maxsize numbytes   Messages larger than this will be ignored as they are
                         unlikely to be spam
    --movehamto mbox     Move ham to folder
    --noninteractive     Prevent interactive requests
    --noreport           Don't include the SpamAssassin report in the message
                         copied to your spam folder
    --nostats            Don't print stat
    --partialrun num     Stop operation after scanning 'num' unseen emails
    --passwdfilename     Use a file to supply the password
    --savepw             Store the password to be used in future runs
    --spamc              Use spamc instead of standalone SpamAssassin binary
    --spaminbox mbox     Name of your spam folder
    --nossl              Don't use SSL to connect to the IMAP server
    --teachonly          Don't search spam, just learn from folders
    --trackfile file     Override the trackfile name
    --verbose            Show IMAP stuff happening
    --version            Show the version information

    (Your inbox will remain untouched unless you specify --flag or --delete)

You can specify your imap password using --imappasswd. This however is a really bad idea since any user on the system can run ps and see the command line arguments. If you really must do it non-interactively then set the password here.

Do your first run.

$ isbg.py --imaphost mail.example.com  --savepw
IMAP password for rogerb@mail.example.com:

The amount of time it takes will be proportional to the size of your inbox. You can specify --verbose if you want to see the gory details of what is going on.

You can now examine your spam folder and will see what spam was detected. You can change the SpamAssassin threshold in your user_prefs file it created earlier.

isbg remembers which messages it has already seen, so that it doesn't process them again every time it is run. If you are testing and do want it to run again, then remove the trackfile (default $HOME/.isbg-track*).

If you specified --savepw then isbg will remember your password the next time you run against the same server with the same username. You should not specify --savepw in future runs unless you want to change the saved password.

Running it

You'll probably want something to actually be done with the original spams in your inbox. By default nothing happens to them, but you have two options available. If you specify --flag then spams will be flagged.

You can get the messages marked for deletion by specifying --delete. If you never want to see them in your inbox, also specify the --expunge option after --delete and they will be removed when isbg logs out of the IMAP server.

Your folder names

Each IMAP implementation names their folders differently, and most IMAP clients manage to hide most of this from you. If your IMAP server is Courier, then your folders are all below INBOX, and use dots to seperate the components.

The UWash server typically has the folders below Mail and uses slash (/) to seperate components.

If you don't know how your IMAP folders are implemented, you can always use the --imaplist option to find out.

How does it work?

IMAP assigns each message in a folder a unique id. isbg scans the folder for messages it hasn't seen before, and for each one, downloads the message and feeds it to SpamAssassin. If SpamAssassin says the message is spam, then the SpamAssassin report is uploaded into your spam folder. Unless you specify the --noreport option, in which case the message is copied from your Inbox to the Spam folder (the copy happens on the IMAP server itself so this option is good if you are on a low bandwidth connection).

Multiple accounts

By default isbg saves the list of seen IMAP message unique IDs in a file in your home directory. It is named .isbg-trackXXXX where XXXX is a 16 byte identifier based on the IMAP host, username and port number. Consequently you can just run isbg against different servers/accounts and it will automatically keep the tracked UIDs seperate. You can override the filename with --trackfile.

To run isbg for multiple accounts one after another, it is possible to use bash scripts like the ones in the folder "bash_scripts". Since these scripts contain passwords and are thus sensitive data, make sure the file permissions are very restrictive.

Saving your password

If you don't want isbg to prompt you for your password each time, you can specify the --savepw option. This will save the password in a file in your home directory. The file is named .isbg-XXXX where XXXX is a 16 byte identifier based on the IMAP host, username and port number (the same as for the multiple accounts description above). You can override the filename with --passwdfilename.

The password is obfuscated, so anyone just looking at the contents won't be able to see what it is. However, if they study the code to isbg then they will be able to figure out how to de-obfuscate it, and recover the original password. (isbg needs the original password each time it is run as well).

Consequently you should regard this as providing minimal protection if someone can read the file.

SSL

isbg can do IMAP over SSL if your version of Python has been compiled with SSL support. Since Python 2.6, SSL comes built in with Python.

However you should be aware that the SSL support does NOT check the certificate name nor validate the issuer. If an attacker can intercept the connection and modify all the packets flowing by, then they will be able to pose as the IMAP server. Other than that, the connection will have the usual security features of SSL.

Exit Codes

When ISBG exits, it uses the exit code to tell you what happened. In general it is zero if all went well, and non-zero if there was a problem. You can turn on additional reporting by using the --exitcodes command line option.

code --exitcodes needed description
0 no All went well
1 yes There was at least one new message, and none of them were spam
2 yes There was at least one new message, and all them were spam
3 yes There were new messages, with at least one spam and one non-spam
10 no There were errors in the command line arguments
11 no The IMAP server reported an error
12 no There was an error of communication between spamc and spamd
20 no The program was not launched in an interactive terminal
30 no There is another instance of isbg running

Read and Seen flags

There are two flags IMAP uses to mark messages, Recent and Seen. Recent is sent to the first IMAP client that connects after a new message is received. Other clients or subsequent connections won't see that flag. The Seen flag is used to mark a message as read. IMAP clients explicitly set Seen when a message is being read.

Pine and some other mailers use the Recent flag to mark new mail. Unfortunately this means that if isbg or any other IMAP client has even looked at the Inbox, the messages won't be shown as new. It really should be using Seen.

The IMAP specification does not permit clients to change the Recent flag.a

Gmail Integration

Gmail has a few unique ways that they interact with a mail client. isbg must be considered to be a client due to interacting with the Gmail servers over IMAP, and thus, should conform to these special requirements for propper integration.

There are two types of deletion on a Gmail server.

Type 1: Move a message to '[Gmail]/Trash' folder.

This "removes all labels" from the message. It will no longer appear in any folders and there will be a single copy located in the trash folder. Gmail will "empty the trash" after the received email message is 30 days old.

You can also do a "Normal IMAP delete" on the message in the trash folder to cause it to be removed permanently without waiting 30 days.

Type 2: Normal IMAP delete flag applied to a message.

This will "remove a single label" from a message. It will no longer appear in the folder it was removed from but will remain in other folders and also in the "All Mail" folder.

Enable Gmail integration mode by passing --gmail in conjunction with --delete on the command line when invoking isbg. These are the features which are tweaked:

  • The --delete command line switch will be modified so that it will result in a Type 1 delete.

  • The --deletehigherthan command line switch will be modified so that it will results in a Type 1 delete.

  • If --learnspambox is used along with the --learnthendestroy option, then a Type 1 delete occurs leaving only a copy of the spam in the Trash.

  • If --learnhambox is used along with the --learnthendestroy option, then a Type 2 delete occurs, only removing the single label.

Reference information was taken from here

Ignored emails

By default, isbg ignores emails that are bigger than 120000 bytes since spam are not often that big. If you ever get emails with score of 0 on 5 (0.0/5.0), it is likely that SpamAssassin is skipping it due to size.

Defaut maximum size can be changed with the use of the --maxsize option.

Partial runs

By default, isbg scans the whole inbox folder. If you want to restrict the number of emails that are scanned, you can use the --partialrun option specifying the number of unseen (not scanned before) emails you want to check.

This may be useful when your inbox has a lot of emails, since deletion and mail tracking are only performed at the end of the run and full scans can take too long.

Contact and about

This software was written by Roger Binns <rogerb@rogerbinns.com> and is maintained by Thomas Lecavelier <thomas@lecavelier.name> since november 2009. With the great help of Anders Jenbo since v0.99.

License

As said by Roger Binns when he hang over isbg to Thomas Lecavelier: " You may use isbg under any OSI approved open source license such as those listed at http://opensource.org/licenses/alphabetical "