Trac Spam Filtering
- How good is the filtering?
- Supported Internal Filtering Strategies
- Supported External Filtering Strategies
- Get the Plugin
- Enabling the Plugin
- SpamFilter and AccountManager
- Further Reading
- Known Issues
This plugin allows different ways to reject contributions that contain spam. It requires at least Trac release 1.0. The source code for version 0.12 and before isn't updated any more, but is still available.
The spamfilter plugin has many options, but most of them are optional. Out of the box the plugin provides basic spam protection. But there are some things which may be helpful in order of importance:
- Train Bayes database using the entries of the log to activate that filter and reach good performance. The Bayes filter requires spambayes.
- Setup BadContent page containing regular expressions to filter.
- Get API keys for Akismet, Mollom, and/or HTTP:BL to use external services.
- Activate captcha rejection handler to improve user treatment; requires reCAPTCHA access when that method is used.
- Finetune the karma settings and parameters for your system, eg you may increase karma for good trained Bayes filters or stop trusting registered users.
- If necessary get API keys for other services and activate them.
WebAdmin is used for configuration, monitoring, and training. For monitoring and training purposes, it optionally logs all activity to a table in the database. Upgrading the environment is necessary to install the database table required for this logging.
How good is the filtering?
The spam filter will never be perfect. You need to check submissions to Trac and improve training or settings of the filter when necessary. But a fine trained setup will help you to run a site even if it is actively spammed, ie thousands of spam attempts a day. Even large sites with completely anonymous edits are possible.
But from time to time spam attacks nevertheless will succeed and handwork is required. Try removing successful spam as fast as possible. The longer it stays in the pages the harder your work will get. Some spammers even monitor successful attempts and retry more intensely.
Spam should be removed completely, also in the page history. Trac has options to delete tickets as well as wiki page versions. If done early enough this does not produce gaps in page history. Spam can also be in uploaded files. Delete them!
Some spam bots edit a page twice, whereby the last change is harmless and the previous one contains the spam. Sometimes spam is done by humans, and while usually successful, humans are easily discouraged by fast deletion.
The Bayes filter when properly trained usually has the best detection rates and can be adapted quickly to new attacks by training the successful spam attempts. Akismet is a good second line of defense and it also uses adaptive algorithms. Training also helps the external service when a new type of attack begins. All other services are good to catch spam inserted through rather dumb methods, which is the majority.
A realistic goal is something like 1 spam for every 10.000 attempts. However, for a new type spam wave, which happens once or twice a year, you have maybe 10-20 slip through at the start of the wave. False rejects should be in the order of one rejection per 1.000 or more successful submissions.
Supported Internal Filtering Strategies
The individual strategies assign scores or "karma" to submitted content, and the total karma determines whether a submission is rejected or not.
The regex filter reads a list of regular expressions from a wiki page named "BadContent", each regular expression being on a separate line inside the first code block on the page, using the Python syntax for regular expressions.
If any of those regular expressions matches the submitted content, the submission will be rejected.
Regular Expressions for IP
The ip_regex filter reads a list of regular expressions from a wiki page named "BadIP", each regular expression being on a separate line inside the first code block on the page, using the Python syntax for regular expressions.
If any of those regular expressions matches the submitters IP, the submission will be rejected.
Regular expressions are much too powerful for the simple task of matching an IP or an IP range, but to keep things simple for users the design is equal to the content based regular expressions. You can even specify full IPV4 addresses, where the dot has special meaning, as the match will work correctly. Only when matching partial addresses more care is needed.
The maximum number of posts per hour is configured in trac.ini:
[spam-filter] max_posts_by_ip = 5
When this limit is exceeded, the filter starts giving submissions negative karma as specified by the
Support for CAPTCHA-style "human" verification is integrated. Captcha usage is configured in the 'Captcha' administration page.
Currently the following captcha types are supported:
- Simple text captcha: Spam robots can bypass these, so they are not recommended.
- Image captcha
- External reCAPTCHA service: To use reCAPTCHA captcha method, you'll need to sign up at https://www.google.com/recaptcha/intro/index.html and set the keys at 'Captcha' administration page.
- External Mollom service. To use this method you need to sign up at Mollom web service and set the keys at 'External' administration page (It's also a spam check service, see below).
The captcha in spamfilter is a rejection system: they are only displayed to the user when otherwise a submission would be rejected as spam. In this case a successful solved captcha can increase the score of a transmission. If a transmission has too many spam points even a successfully solved captcha can't save it, ie the score is 30 and a captcha only removed 20 points.
The Bayes filter is a very powerful tool when trained and used properly:
- When beginning, the filter needs a minimum amount of 25 entries for HAM (useful entries) and also for SPAM (advertising). Simply train every submission you get until these limits are reached.
- The training is done in Administration Menu "Spam Filtering / Monitoring". You have following buttons:
- Mark selected as Spam - Mark the entries as SPAM and train them in Bayes database (not visible by default for newer versions)
- Mark selected as Ham - Mark the entries as HAM and train them in Bayes database (not visible by default for newer versions)
- Delete selected - remove entry without training
- Delete selected as Spam - Mark the entries as SPAM and train them in Bayes database, remove them afterwards
- Delete selected as Ham - Mark the entries as HAM and train them in Bayes database, remove them afterwards
- Rules for a good trained database are:
- Don't train the same stuff multiple times
- HAM and SPAM count should be nearly equal; in reality you will have more SPAM, but a ratio of 1 to 5 should be the maximum
- Start from scratch when results are poor
- It is hard to get rid of training errors, so be careful
- See SpamBayes pages for more details.
- Strategy for Trac usage:
- Use the Delete selected as Spam and Delete selected as Ham
- Remove every strange entry using Delete selected, eg SandBox stuff
- Train every valid HAM entry or the database will get unbalanced
- Be sure to train every error: Rejected user submissions as well as undetected SPAM
- Train every SPAM entry with a score below 90%; at the beginning you may train everything not 100%
- Delete SPAM entries with high score; 100% in any case, after beginning phase everything above 90%
- When in doubt if SPAM or HAM, delete entry
- NOTE: When Akismet, BlogSpam or StopForumSpam (with API key) are activated, then training will send the entries also to these services.
- If you append the parameter "num" with values between 5 and 150 at monitoring page
url.../admin/spamfilter/monitor?num=100you can show more entries, but don't train with a very large dataset at once.
Supported External Filtering Strategies
See SpamLinks DNS Lists for a list of DNS based blacklists. A blacklist usable for this filter must return an IP for listed entries and no IP (NXDOMAIN) for unlisted entries.
NOTE: The submitters IP is sent to the configured servers.
See SpamLinks URL Lists for a list of URL based blacklists. A blacklist usable for this filter must return an IP for listed entries and no IP (NXDOMAIN) for unlisted entries.
NOTE: Domain links submitted in the transmission are sent to the configured servers.
The use of this filter requires a Wordpress API key. The API key is configured in the 'External' administration page.
NOTE: Submitted content is sent to Akismet servers. Don't use this in private environments.
The use of this filter requires API keys. These API keys are configured in the 'External' administration page.
NOTE: Submitted content is sent to Mollom servers. Don't use this in private environments.
Training this filter requires an API key. The API key is configured in the 'External' administration page.
NOTE: Submitted username and IP is sent to StopForumSpam servers. Don't use this in private environments.
This service includes also DNS checks and services identical to the checks in this plugin. Be sure to set proper karma or these checks are counted twice. You also can disable individual checks in preferences.
NOTE: Submitted content is sent to BlogSpam servers. Don't use this in private environments.
The use of this filter requires a HTTP:BL API key. The API key is configured in the 'External' administration page.
NOTE: Submitters IP is sent to HTTP:BL servers.
Using this filter requires an API key. The API key is configured in the 'External' administration page.
NOTE: Submitted username and IP is sent to BotScout servers. Don't use this in private environments.
Using this filter requires an API key. The API key is configured in the 'External' administration page.
NOTE: Submitted username and IP is sent to FSpamList servers. Don't use this in private environments.
Get the Plugin
You can also obtain the code from the Trac Subversion repository:
svn co http://svn.edgewall.com/repos/trac/plugins/1.0/spam-filter
See TracPlugins for instructions on building and installing plugins.
Enabling the Plugin
[components] tracspamfilter.* = enabled
You can disable individual strategies:
- Disable the corresponding class in plugin handling
- Set karma to 0
- External services requiring API key are disabled without key
- All external services can be disabled in 'External' section (completely and only for training)
The Spamfilter adds new permissions to Trac:
|SPAM_CHECKREPORTS||Allows to review and delete user spam reports|
|SPAM_CONFIG||Get the admin menu entries to configure the filter|
|SPAM_MONITOR||Get the admin menu entries to monitor the submissions (spam or ham)|
|SPAM_REPORT||Add link to report spam to pages, so user can submit pages as spam to the admins|
|SPAM_TRAIN||In the monitoring panel access the spam training functions (useless without SPAM_MONITOR)|
|SPAM_USER||Enables user evaluation display which allows to detect and delete inactive accounts|
|SPAM_ADMIN||Combination of all six|
The permission SPAM_REPORT should probably not be assigned to unauthenticated users or else there will be many false reports. Minimum in this case should be to exclude '/reportspam' URL in robots.txt file.
SpamFilter and AccountManager
If the AccountManager plugin is used in version 0.4 or better, then registrations can be checked for spam as well. To do so, the entry RegistrationFilterAdapter needs to be added to key register_check in section account-manager of trac config. There are several ways to do this:
- Add it as first in the line: the filter then displays reject reasons in the spamfilter log.
- Add it as last in line: first are the accountmanager checks and only if all is fine, then the spamfilter is called.
- Enable the "account_replace_checks" to let spamfilter perform the Accountmanager checks (not recommended).
Newer versions of AccountManager have a configuration dialog to do necessary setup to enable the RegistrationFilterAdapter.
The SpamFilter plugin has several modules to check the contributions of users, find inactive and delete unwanted users. To delete users, the corresponding AccountManager modules are called.
You can translate the plugin into your language: https://www.transifex.com/projects/p/Trac_Plugin-L10N/resource/spamfilter/
Top translations: Trac_Plugin-L10N » spamfilter
- Historic information about SpamFilter: Managing Trac Spam
Attention: dnspython v1.7 causes a massive slowdown of the Trac site.
- The modules for IP blacklisting and HTTP:BL require dnspython v1.8+. Install "setuptools" of the Trac plugin requirements, then run
easy_install dnspythonto install the package.
- The ImageCaptcha requires python-imaging to work.
- Bayes filtering requires spambayes.
- Mollom filter requires python-oauth2.