The advisory urges critical infrastructure operators to secure their operational technology and control systems as soon as possible.
The advisory lists several “recently observed tactics, techniques, and procedures,” including spear phishing, ransomware, connecting to Internet-accessible PLCs that do not require authorization for initial access, and modifying control logic and parameters on PLCs.
Here is a link to Defense.gov with the full warning text: (PDF)
https://media.defense.gov/2020/Jul/23/2002462846/-1/-1/1/OT_ADVISORY-DUAL-OFFICIAL-20200722.PDF