Please help to identify the following description belonging to which technique in MITRE and the corresponding tactics: Magic Hound has exploited the Log4j utility (CVE-2021-44228), on-premises MS Exchange servers via "ProxyShell" (CVE-2021-34473, CVE-2021-34523, CVE-2021-31207), and Fortios SSL VPNs (CVE-2018-13379).