Hello. The safety of salo is based on the curing process and modern food production standards. The primary risk in undercooked pork is the parasite Trichinella. However, there are two main ways this risk is eliminated for a product like salo.
First, the curing proccess. A high concentration of salt is used, which draws water out of the fat and any microorganisms within it, including parasites. This dehydration is lethal to them.
Second, and just as important, is the source of the pork. In most of the EU, pig farming is highly regulated to prevent Trichinella infection in the first place. The parasite is now extremely rare in commerical pork. Often, as an additional precaution, the pork belly is frozen at a specific temperature for a set period (for example, -15°C for 30 days) before or during curing, which also effectively kills any potential parasites.
Therefore, if the salo is from a reputable producer, the risk is negligible and it is considered safe to eat raw.