OxCERT blog describes Dridex as "an evasive, information-stealing malware variant; its goal is to acquire as many credentials as possible and return them via an encrypted tunnel to a Command-and-Control (C&C) server. These C&C servers are numerous and scattered all over the Internet, if the malware cannot reach one server it will try another. For this reason, network-based measures such as blocking the C&C IPs is effective only in the short-term."
According to MalwareBytes, "Dridex uses an older tactic of infection by attaching a Word document that utilizes macros to install malware. However, once new versions of Microsoft Office came out and users generally updated, such a threat subsided because it was no longer simple to infect a user with this method."
IBM X-Force discovered "a new version of the Dridex banking Trojan that takes advantage of a code injection technique called AtomBombing to infect systems. AtomBombing is a technique for injecting malicious code into the 'atom tables' that almost all versions of Windows uses to store certain application data. It is a variation of typical code injection attacks that take advantage of input validation errors to insert and to execute malicious code in a legitimate process or application. Dridex v4 is the first malware that uses the AtomBombing process to try and infect systems."