Whoever uses an analog/ISDN line (modem) risks running into malicious dialers, which establish unwanted connections with expensive per-minute charges.
Downloading logos, ringtones, software, mp3 files or porn can be dangerous. It is a fraud that circulates on the internet and is carried out with small software, called dialers, which access our computers through emails or banners.
It is enough to click on a dubious banner unintentionally or open an unknown email to start the automatic installation of the dialer, that in most cases is totally hidden.
Recently the most malicious attackers have been exploiting Internet Explorer security certificates (used by 90% of Internet users), so that it is enough to accept a security certificate like the one below to be caught by the malicious dialer:
Figure 1: Internet Explorer security certificate
Malicious dialer programs may connect by default a user's computer to expensive toll numbers (usually starting with 709, 166, 899) or to long distance numbers giving access to reserved areas. The average cost of a call is around 2.5 euros per minute. This means that to get 10 ringtones (downloadable in around 60 minutes) you could pay up to 180 euros.
The scam works like this: price information is made invisible and a software is installed on your PC which dials a number almost automatically.
Sometimes the victims may be totally unaware of the dialer's presence until they get their telephone bills.
For these reasons it is advisable to take the following steps:
If you clickon a link or a banner and you are asked to download a file with extension .exe to gain access to special content,you have probably run into a malicious dialer. In this case just click "cancel" and you will be safe.
If you want to download a logo, a ringtone, an mp3 file, or a porn picture, the probability that you run into a malicious dialeris even higher.
A file protection warning popup may appear when opening a website, which invites you to install a protection certificate. If this happens, click "No". It would be enough to click on "Yes" to be disconnected and reconnected to a pay telephone line.
You can ask your telephone operator to block899, 709, 166 numbers and all other expensive toll numbers.
It is advisable to install a software, which is capable of blocking other phone numbers, as the one below:
Figure 2: Dialer Control's main interface
This software is a fundamental tool for neophyte internet users as it is always harder to understand whether a website offers freeware or
chargeable contents through a dialer.
When the user tries to establish the first connection the software realizes what is happening and informs the user by submitting the following request:
Figure 3: Software request
At this point the user can decide whether to authorize the connection or establish a rule for the future. If the user chooses "Yes" ("Si") answering the question "Do you want to continue?" ("Vuoi continuare?") the connection will be created but the rule for the future not be established and the program will ask the same question at the next connection. On the other hand, if you want to set a rule, so that the program does not need to ask for permission every time, you just have to choose one of the options suggested.
If the connection you are using is the same as the one used for netsurfing you have to select the button "Always allow access to this software" ("permettere sempre gli accessi a questo software") and also "to this number" ("a questo numero"). This way, you authorize a connection using a single telephone number. Once the rules have been set, it is possible to check them on the program main interface through the button "Allow" ("Permetti").
There is also a lot of free software available on the Internet, as the one we have described, which prevent modem connection to phone numbers other than your provider's numbers.