Thursday, April 25, 2019

How to prevent VOIP Spam

What is SPIT?

Spam over Internet Telephony (SPIT) is telephone spam that is transmitted over the Internet Protocol using IP (Voice over IP) telephony. Telephone spam refers to unwanted telephone calls that are automatically and in large numbers recorded. Phone spam is similar to email spam, but is currently less common and requires other safeguards due to synchronous communication.

How abuse takes place

IP telephony, as well as email and other Internet applications, is prone to being abused by unwanted messages and connections. Call machines can be used for telesales, telemarketers, for alleged winning messages, or as phone calls. In particular, IP telephony offers this freely available software (such as Asterisk or SIP) and inexpensive options to automatically sell a large number of calls. The IP telephony is often based on the Session Initiation Protocol (SIP) [1] for setting up, controlling and reducing the telephone connections. After establishing a SIP session and accepting the call by the called party, a pre-recorded spam message can be recorded. For pure lock or ping calls, no audio data is transmitted.

Large numbers of unwanted and automated phone calls

SPIT is characterized by a large number of unwanted and automated phone calls that are transmitted using the Internet Protocol. The caller (spammer) tries to establish a large number of connections using suitable software and plays a recorded message as soon as the called party answers the call. Using the widely used Session Initiation Protocol (SIP), the connections to INVITE messages are initiated and then configured and set up with other messages; The audio data is then transmitted via the Real-time Transport Protocol (RTP). The spammer can this telephony software such. B. Asterisk use. The spam calls can be transmitted via gateways of the telecommunications network operators in the conventional telephone network (PSTN).

How to prevent VOIP Spam?

Many users have no problem with SPIT already being "shielded" behind NAT or a package filter, AKA firewall. Others, running a Linux server with VOIP server and client on it might be exposed to VOIP Spam. These can protect themselves by setting up one package filter rule:

iptables -A INPUT -p udp ! -s 217.10.79/24 --destination-port 5060 -j REJECT
assuming 217.10/16 is the IP range from your ISP. In this case it's Sipgate. That will throw away all UDP packages to the SIP port (5060, might differ on other setups) unless they come from 217.10.79/24.

Tuesday, April 9, 2019

How to disable auto play of videos in Chrome and Firefox browsers

When users enter certain web pages, often videos embedded there start to play automatically. Many users, including me, do not wish to run videos they didn't demand. But they play anyway. Is there a way in Browsers like Chrome or Mozilla's Firefox to deactivate the automatic play of videos? Besides it's annoying, these videos use data. When a user has a "cap" with his ISP (the maximal amount of data he can transfer every month) he might pay additional charges for a data transfer, he didn't demand. Luckily for web browser like Mozilla's Firefox and Google's Chrome there is a way, to deactivate the automatic playing of videos, like in Youtube.

Chrome and Chromium web browsers

The Chrome web browser is currently the dominant browser and holds the biggest market share. Thanks to the implementation in Android smart phones and tablets, Android ships.

Desktop

After launching the browser click into the address bar on top and type in about: flags and hit the RETURN key. On top you find a search form. Enter autoplay and click on the first find the drop down menu and choose Document user activation is required. After you restart Chrome videos should not start automatically anymore, but asks the user to confirm, he wants to run a particular video.

Chrome on Android

This is easier. Launch the Chrome browser on your tablet or smart phone and visit Settings and then Site Settings. Scroll down the media menu and select the media tab. There you must select autoplay and click the checkbox, to disable the function.

Mozilla's Firefox

The Firefox browser of Mozilla has some great features. It is highly customizable. It has among other native features the ability, to prevent videos from starting to play automatically. Click the URL bar and type in about:config. Ignore the warning and use the search form to find media.autoplay.default. Set this to "1" if it was not already set. Also find media.autoplay.allow-muted and set this to false. Restart the Firefox browser that the changes take effect

Other methods

If this isn't working for you, third party add-ons come into play. Open the Preferences menu and search for addons or extensions. There is a search form. Search for something like disable, auto play or automatic and install the appropriate extension.