I am going to close this topic as only the latest phpBB release (at the time of this writing is phpBB 3.0.6) is supported. At this time, any spam prevention posts will be met with a suggestion to upgrade to phpBB 3.0.6.
This topic will be preserved for the sake of archiving.
Preventing Spam in phpBB 3.0.6
Though phpBB 3.0.5 does include various changes to the CAPTCHA that help deter spambots, it is an unfortunate fact that any fix that is included in the standard software package will quickly be broken. As a result of that, your best bet is to make your board unique (relative to the standard package). The MODs and other tweaks below will aid you with this.
- What is a spam bot?
Simply put, a spam bot (with relation to phpBB) is a script that is able to register an account and/or post spam on your board.
- Is spam a security threat?
No. While spammers may seem like they are breaking through your defenses, they actually don't do anything that a regular users couldn't do (register, post, etc). Spam is therefore not a vulnerability and should not be considered as such.
- How do they work?
Spam bots do what they are programmed to do; nothing more. Not having the ability to adapt on the fly puts bots at a disadvantage when put against informed administrators such as yourself. The trick for dealing with bots is to stay one step ahead of their authors. Nearly all anti-spam MODs focus on changing the registration/posting form in order to prevent bots from being able to fill out the information properly.
- Do bots fill in the form the same way humans do?
No, the majority of bots submit their responses directly, without loading the form that you set up. What this means in practical terms is that changing only the HTML form will not do anything; you need to actually change how the passed information is interpreted (that means editing the .php files). If you encounter MODs that only edit HTML, they are pointless.
- Should I ban bots by IP or email TLD (.ru, .info, etc.)?
If your goal is to save time, this strategy will not help. IPs are often cycled and there are thousands of available proxies that can be found just by searching. By banning IPs, you will also end up banning legitimate users. As bots use a variety of TLDs for their email accounts (including .com, .org and .net), banning international ones like .ru may help slightly, but you will once again end up banning legitimate users (and won't ban nearly every bot). In short, you should focus on preventing as many bots as possible, while not causing legitimate users too much extra hassle.
- What about human spammers?
Fighting human spammers is more difficult than fighting bots. While bots will blindly attempt to register and post on every board possible, human spammers will want to make sure that their spam is actually being seen. The trick to fighting human spammers, therefore, is to remove any incentive they would have of targeting your board.
- Will following this guide stop all spam?
As I said above, human spammers are difficult to stop and some bots may be adapted to work on your site. Following this guide will, however, cause a significant decrease in the amount of spam starting from the very first day
- CAPTCHA - While some bots have been able to break the stock CAPTCHA, it does remain effective at stopping poorly written bots. The changes in 3.0.5 enable some additional settings that make the CAPTCHA slightly more effective. Do keep in mind, however, that these settings make the CAPTCHA more difficult to read, also impacting human users. Therefore, it is recommended that you tweak the CAPTCHA slightly and enable another form of spam protection to stop bots that are not stopped by the CAPTCHA. An effective CAPTCHA setup will have the CAPTCHA background X and Y axis lowered. Additionally, 3D-noise objects should be enabled and an alternate font should be selected.
- Custom Profile Fields - There is an article in the Knowledge Base detailing utilising Custom Profile Fields as a spam deterrent. This seems to be effective against most bots.
- Admin Activation - This is not practical on most boards, but is an excellent option on smaller, less-trafficed boards. Many spam registrations utilise Gmail addresses or .cn domains, and use a seemingly random combination of letters and numbers for their username.
- Post Queueing - phpBB 3.0.3 introduced a new feature which allows admins to queue posts if the users post count is lower than a defined value.
Administration Control Panel > General > Post Settings > Enable queued posts.
This means that your users will not see the first X number of posts by spam accounts and you can remove them and deactivate the accounts without disruption to your members, but legitimate users will be free to post once that number of posts has been approved.
- MODs - The best option to stop spam is to make your board somewhat unique, by using deterrents like MODs that are not implemented in a stock phpBB3 install. Below are a list of MODs that do just this. If you are a MOD Author and believe your MOD should be listed here, please PM me or another Support Team Member. Please note that many anti-spam MODs will cease functioning following the release of phpBB 3.0.6 due to changes in the CAPTCHA/registration architecture.
- Advanced Block MOD by Martin Truckenbrodt - "Adds multiple DNS Blacklists, Adds timezone check (UTC -12 trick), adds Block log for block actions"
- Advanced Visual Anti Bot by lsjames - "Advanced Visual Anti Bot is an effective solution for preventing spambot. It replace the default visual confirmation background with a random picture. So spambot can not check them out by OCR. The background pictures are replaceable. Advanced Visual Anti Bot does not require any database modifications or admin panel configuration."
- Anti-Bot Question by CoC - "Add an Admin controlled anti-bot question to the registration page and ACP."
- Anti-Spam ACP by EXreaction - "Anti-Spam ACP adds many powerful anti-spam features to your forum such as an IP Search tool, Spam Word list, control over profile fields, flagging suspicious users (for logging their actions), and an easy one click ban link from their profile which clears out their profile and posts."
- daroPL_AntiSpam by daroPL - "MOD blocks spambot registrations on board via change name of confirm code field to unique hash. In addition, it changes size of confirm code field to random."
- Automatic Spammer Detection by mtotheikle - "This MOD uses Stop Forums Spam and Bot Scout to check username, email and IP for potential spammer. If anything is returned, all the founders receive a PM notify them about the user. Has ACP settings to disable/enable mod and set what sites to check." *This MOD has NOT been validated by the MOD Team*
- Prime Anti-bot by primehalo - "Implements a text-based human validation system in order to verify that a form submitter is human and not a SPAM robot. It will remember a successful validation so the user won't have to re-validate each time. The validation phrases/questions and responses are fully customizable; you can put as many or as few as you want (one is picked from the list at random each time it's needed). Can be configured to validate on new registrations and guest postings." *This MOD has NOT been validated by the MOD Team*
1234323325 - iWisdom - original version
1234408584 - iWisdom - add AntiSpamBot by Timezone to MODs
1234517666 - Kevin Clark - add 3DCaptcha Olympus to MODs
1234865852 - Kevin Clark - add daroPL_AntiSpam to MODs
1236071812 - Kevin Clark - add post queueing info
1238031183 - iWisdom - remove abandoned MODs
1239761265 - iWisdom - add Advanced Visual Anti Bot to MODs
1242837505 - stevemaury - daroPL AntiSpam now validated
1243094851 - stevemaury - corrected "Exreacion"
1243799509 - iWisdom - add note on CAPTCHA due to 3.0.5 update
1243801592 - iWisdom - add JScript Anti Bot to MODs
1248315477 - iWisdom - add note with regards to CAPTCHA architecture and 3.0.6 breaking existing MODs
1249185906 - iWisdom - move Antispam ACP to validated
1252280498 - iWisdom - add Advanced Block MOD to MODs
1258587752 - iWisdom - retired