That is an NTE5 master socket. Putting microfilters on every extension independently is not a good way and you will suffer some loss of speed unless you are very close to the exchange or cabinet (depending if you are on ADSL or VDSL). With VDSL it can be particularly bad.
A couple of bits of information would be extremely useful. One is whether you are using ADSL or VDSL (fibre to the cabinet) services. The second is the line stats information from your router/modem, and especially sync speeds, noise margin and attenuation numbers.
A good test to do is to remove the faceplate on your NTE5 master. That can be pulled clear which should isolate all the extensions. There will be a test socket visible and temporarily plug your modem/router in there as that eliminates any problems caused by domestic wiring. It gives a baseline. Again get the line stats off your modem/router and these can be compared with what you are seeing currently.
If it turns out that the domestic wiring is causing problems with your broadband speed, there are a number of things that can be done ranging from the trivial (disconnecting the ring line extension connections at the mast) to a fitting of a filtered faceplate.
If you connect your modem/router at the master, then the simplest fix is simply to but and install an Interstitial plate, which can be fitted without any wiring modifications at all (but you BB will only work from the master). There are more sophisticated solutions which can be used if you want your modem/router to be installed on an extension, although that requires more work.
This is an OR Interstitial plate. Note that it can be used to provide an unfiltered BB extension as well, but that requires a wiring modification.