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Keeping Telemarketers At Bay With TrixBox and freePBX-Enabled Asterisk Systems

Just when you thought the National Do-Not-Call Registry was getting you some peace and quiet during the dinner hour, VoIP telephony comes into its own and gives the telemarketers a brand new universe to pollute. And, of course, the politicians exempted themselves and non-profits from the Do-Not-Call rules anyway. So the unwanted dinnertime calls from your best friends at campaign headquarters and the Fraternal Order of Police will always need to be dealt with. Lucky for all of us, there’s an Asterisk® PBX standing between the telemarketers and the dinner table. We first wrote about this 16 months ago so we wanted to provide an update showing how much simpler things have become with TrixBox and any other Asterisk system running freePBX 2.2.x. In the "old days" you had to do a good bit of mucking around in the Asterisk code to blacklist callers. And that method still works. However, you now can avoid the coding knuckle drill. With the latest versions of freePBX, you can send a special information tone to certain callers to block autodialers just by adding the unwanted numbers to your BlackList. There’s no code to modify at all. And there are three simple ways to manage your blacklist. Here’s how.

BlackListing Callers With freePBX. freePBX 2.2.x now includes all the tools you’ll need to block unwanted calls. If you’re running one of the free TrixBox 1.2.3 systems at the top of this page, we’ve already provided a tutorial to get your freePBX system upgraded. Once you’ve done that or if your running TrixBox 2.x, to block calls from unlisted numbers, simply log into freePBX and choose Setup, General Settings, and set Allow Anonymous Inbound SIP Calls to No. This may cause too many calls to be blocked with some hosting providers. Another option is to set Privacy Manager to Yes in each of your Inbound Routes setups. This forces Asterisk to prompt callers for their phone number when no CallerID is provided. If there are old girlfriends and ex-wives that you’d prefer to never hear from again, choose Setup, Blacklist, and plug in the numbers. When they call, they’ll be greeted by a disconnect tone and a message that your number is no longer in service. It’s as simple as that. If you change your mind, you can remove numbers from your blacklist just as easily. freePBX now displays the list of all the numbers you’ve blacklisted. Just click Delete beside the number you wish to remove from your blacklist, and you’re done. It doesn’t get much easier than that.

BlackListing Callers Using Your Phone. You may not always want to run to your computer to block future calls from someone that annoys you. freePBX now includes built-in support for blacklisting callers using any telephone on your Asterisk system. If you’ve just hung up and wish to blacklist the last caller, pick up your telephone and dial *32. You’re done. If you want to manually enter a different number into your blacklist, pick up any phone on your system and dial *30. Enter the number to be blacklisted when prompted. To remove a number from your blacklist, dial *31 and enter the number to be removed.

BlackListing Callers Using Phone Genie for Asterisk. If you’ve installed our free Phone Genie for Asterisk web utility, you also can blacklist callers by sending an HTML command to your Asterisk server using any web browser including the one on your cellphone.

To add a number to your blacklist, just enter a command like this where 192.168.0.123 is the IP address or fully-qualified domain name of your Asterisk server, 6781234567 is the number to be blacklisted, and 1234 is your admin password for Phone Genie:

http://192.168.0.123/nv-genie.php?action=dbput&family=blacklist&key=6781234567&value=1&pw=1234

To remove the same number from your blacklist, the web command would look like the following:

http://192.168.0.123/nv-genie.php?action=dbdel&family=blacklist&key=6781234567&pw=1234

To display the numbers in your blacklist, the web command would look like the following:

http://192.168.0.123/nv-genie.php?action=dbshow&family=blacklist&pw=1234

You’re an expert now. So just sit back and wait for the Bad Guys to call. They will.

Our Special Thanks. We’re actually out cruising in the middle of the Carribean this week soaking up a little sun. So don’t be frustrated if your comments don’t get posted until next week. We did want to take a moment to thank all you for reading Nerd Vittles. About 50,000 folks from 137 countries around the globe read Nerd Vittles every week. The Nerd Vittles Official Flag at left shows all of your home towns, and that’s just this month. Incidentally, the countries are ordered by the number of actual visitors from each country. We like detail work unfortunately. InfoWorld finally discovered Open Source VoIP this week, and Vonage would do well to brush up on the advantages of open source VoIP… within the next two weeks. The VoIP Revolution is, of course, old news to us and to you. But it does demonstrate that our little secret is becoming front page news worldwide almost every day. Thanks again for your support. And, yes, we’re still looking for a few good advertisers. You don’t get a huge ad, but you get an enormous, focused, loyal group of readers. And we’ve got the cheapest ads on the planet, just $500 a month. Give it a shot. You won’t be disappointed, and you’ll be helping us hire some H-E-L-P, not to mention paying for these Carribean junkets.

Security Reminder. If the version of Asterisk displayed when you start up the Command Line Interface (asterisk -r) predates Asterisk 1.2.17, your system is extremely vulnerable to a SIP denial of service attack. For complete upgrade instructions, read this Nerd Vittles article.


trixbox Appliance. In case you missed it, Fonality has announced a new line of turnkey trixbox appliances. Two-port and six-port configurations as well as models with one and two preconfigured T1’s, mirrored drives, and redundant power supplies will be available for purchase in June starting at $999 for the base model. Stay tuned to Nerd Vittles for a sneak peak and test drive of what’s coming. In the meantime, you can read all about the new line of trixbox appliances by clicking on the link at the top of the page. Great idea!


Nerd Vittles Demo Hot Line (courtesy of les.net). You now can take a number of Nerd Vittles projects for a test drive… by phone! The current demos include (1) MailCall for Asterisk with password 1111 (retrieve your email by phone), (2) NewsClips for Asterisk (latest news headlines in dozens of categories), (3) Weather Forecasts by U.S. Airport Code, and (4) Weather Forecasts by U.S. ZIP Code. You’re not prompted for #4 yet, but it does work! Just call our number (shown in the left margin) and take any or all of them for a spin. The sound quality may not be perfect due to performance limitations of our ancient Intel 386 demo machine. But the price is right.

Nerd Vittles Fan Club Map. Thanks for visiting! We hope you’ll take a second and add yourself to our Frappr World Map compliments of Google. In making your entry, you can choose an icon: guy, gal, nerd, or geek. For those that don’t know the difference in the last two, here’s the best definition we’ve found: "a nerd is very similar to a geek, but with more RAM and a faster modem." We’re always looking for the best BBQ joints on the planet. So, if you know of one, add it to the map while you’re visiting as well.


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1 Comment

  1. The SIT tone is "long long long", it should be short short long, meaning "disconnected". I wonder why the DAHDI drivers were compiled like this instead of the short short long like one would think? Interesting.

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