Ransomware gangs are increasingly buying their way into corporate networks, purchasing access from vendors that have previously installed backdoors on targets. Researchers from Proofpoint have uncovered a lucrative criminal ecosystem that works together to mount successful ransomware attacks. The relationship between threat actors and ransomware groups is not one-to-one, however, as multiple threat actors use the same payloads for ransomware distribution. About 20 percent of the malware seen in the first half of 2021 infiltrating networks this way.
Source: https://threatpost.com/booming-cyber-underground-market-initial-access-brokers/166965/