How do mobile companies deal with pseudo base stations?

In fact, as early as the beginning of August this year, there was a round of "pseudo base station" cases, and there were countless previous cases. Because the incident was quite noisy at that time, we also reported it, sorted out the relevant contents of the "pseudo base station" for everyone, and analyzed its workflow from a technical point of view (see recommended reading), but did not talk about how to restrain it. Recently, a statistic that "the total amount of spam messages in China in the first half of this year exceeded 200 billion" once again pushed the source "pseudo base station" to the forefront.

It is recommended to watch Pseudo Base Station. It takes 23,000 seconds to block the carrier network.

However, we found that as long as we stay out of the limelight, "pseudo base stations" will still appear, which is as difficult to eradicate as Xiao Qiang. Among them, "commodity demand" is easily overlooked. As the saying goes, "flies don't bite seamless eggs", or someone needs this thing, "pseudo base stations" will be so rampant.

On the other hand, since this figure can be counted, why can't it be shielded and contained? The following content may not be able to treat both the symptoms and the root causes, but it does provide us with a seemingly feasible method.

Disclaimer: The following contents are compilation records.

The current pseudo base stations are all GSM pseudo base stations, mainly because of the high penetration rate of GSM network, many users and imperfect protection of GSM network. Let's briefly draw the workflow of the pseudo base station:

It can be seen that the pseudo base station first suppresses the signals of the surrounding GSM cells with high-power broadcast signals, which makes the surrounding mobile phones switch doors to the pseudo base station because of the difference in signal strength. The pseudo base station will also broadcast a very unique number, so that the mobile phone finds that it has entered a new area and needs to re-register its location.

In the location registration stage, the pseudo base station simulates the real base station, interacts with the mobile phone, implements the authentication process, and obtains the IMSI of the mobile phone user. IMSI is the unique identification of the whole network of mobile phone users, which can be understood as the ID number. After the location registration is completed, the pseudo base station uses the obtained IMSI to page the terminal. After the terminal responds, the pseudo base station sends a short message, and the calling number in the short message uses a forged number to deceive the user.

However, the so-called magic height is one foot and the road height is ten feet. Naturally, there are solutions.

Constraint method

One way is for operators to strengthen mobile networks so that the coverage of pseudo base stations will never be stronger than that of mobile networks. This is obviously a stupid method. At present, the power of the pseudo base station has reached the level of 10W. If the operator's network is upgraded to this level, regardless of the feasibility of building a station, optical electromagnetic radiation is enough to make people flinch.

Another method is to improve the location registration process of mobile networks. In the authentication process, not only the network authenticates the terminal, but also the terminal authenticates the network. This new authentication method has been implemented in WCDMA and other networks, but it is very difficult to transform in GSM network.

In the case that GSM network will continue to serve, what simple methods can we have to prevent pseudo base stations from sending spam messages?

There is another method, that is, although the mobile phone receives spam messages, it does not display them, which also achieves the effect of suppressing pseudo base stations. Of course, this is an expedient measure, and the best way is to upgrade the GSM network.

How to prevent spam messages from being displayed? Here I introduce a processing idea.

It can be seen from the working principle of the pseudo base station that the pseudo base station can only obtain the IMSI of the mobile phone, but not the number of the mobile phone. That is, I only know the ID number, not the name. So we can ask to add a field in the short message, which is the called number. Using the called number, the mobile phone can check whether it is sent to itself, and delete it if it does not meet the requirements, so that there is no chance for spam messages to appear.

This method involves the transformation of short message center, and needs to add a judgment on the short message function of mobile phone. If it is a smart phone, it should be very convenient to implement.