Career / Leadership

4 Ways to Block Spam Calls with Cisco Call Manager

by Team Nuggets
4 Ways to Block Spam Calls with Cisco Call Manager picture: A
Published on October 29, 2018

No one likes spam calls, especially at work. They kill productivity, jam phone lines, and they're just plain annoying.

Collaboration admins are the front line in the fight against spammers. But it's one person against legion, and one person can only do so much.

Luckily, we have some good solutions with the aid of CUCM (aka Cisco Call Manager) to help you cut through the waves of spam calls.

Block all anonymous calls

If you are like most people, seeing the "Private Number" or "Unknown" on your office phone's isn't the biggest deal. They're simple to ignore. But why ignore when you can block?

Spam calls tend to display non-numerically, which is easy to filter out. Create a translation rule blocking CIDs that contain anything but a number.

rule 2 reject /[^0-9]/ rule 2 reject /^[^0-9]/ rule 2 reject /[^0-9]$/"

CUCM can take any of these commands to make your anonymous callers a thing of the past.

A disclaimer: We'd recommend that you test this rule before executing it. You don't want to end up blocking customers or clients.

Use translation rules to block individual numbers

Translation rules can block individual numbers, too. Take the example below.

router(config-xxx)#rule 1 reject /##########/

Disclaimer #1: This solution is not fun to set up. It's your goal to make less work for yourself. Not more. Individually blocking every spammer is a Sisyphean challenge. But hey, at least it provides a little job security for collaboration engineers.

Disclaimer #2: You also need to be careful with translation rules in general. They can slow down your network. When a call comes in, CUCM has to sort through all the rules. This isn't a problem for smaller setups.

Use translation patterns to block groups of numbers

Translation patterns are another good way to block unwanted callers. They're a little more complicated, but they're really effective for blocking groups of numbers.

Disclaimer #1: Translation patterns come at a price — hard disk space. HDD isn't as big a problem as it used to be. But it's still a thing to consider, especially if you have a really big telephone footprint across the enterprise.

Disclaimer #2: Take into consideration the fact that translation patterns are not an intelligently driven technology. In fact, they're kind of dumb. Use them sparingly and with plenty of caution if you don't want to accidentally block legitimate calls and slow down your system. Read up as much as you can about translation rules. Or watch CBT Nuggets trainer Chuck Keith explain how to use translation patterns properly.

Remove all your connections to the PSTN

The sheer volume of the spam calls is shocking. More than half of calls in 2018 were spam calls. So, just shut it down. Seriously. Take it offline, and don't let anything through that you don't know.

This may sound a little extreme but think about it. How much business you are actually conducting through your PSTN? The UK is already shutting down their PSTN and IDNS in 2025, and the United States is soon to follow.  

Focus on the core function of your telephony system and create a barrier between you and the spammers. If you are getting a large proportion of spam calls coming through into your organization, this could be an option for you.  

Just don't have phones at all

You read that right, just get rid of them! A recurring theme among millennials is their avoidance of verbal communication technologies.

This is obviously by no means a reasonable strategy for a traditionally structured company that relies on telephones to conduct their daily operations, but for youthful start-ups with limited capital, it might be the only option that makes financial sense.

There's no single way to kill spam calls

As you have no doubt gathered by this point, the anti-spam crusade is, for the most part, a slow and manual process.

There's no single solution to the irksome issue of spam calls, but Cisco Call Manager is a powerful collaboration platform with plenty of options for blocking unwanted calls.

The overall options and configurations that can be set up with CUCM are staggering. With a little experimentation, you can devise a cunning plan to stop the spam callers without accidentally alienating everyone else.


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