The Arizona State Bar Association has issued an advisory ethics opinion approving of lawyers’ use of encrypted online storage services to store client information. See Az. State Bar Op. 09-04 (Dec. 2009). The opinion, however, warns lawyers to keep informed of technological developments:

Lawyers providing an online file storage and retrieval system for client access of documents must take reasonable precautions to protect the security and confidentiality of client documents and information. Lawyers should be aware of limitations in their competence regarding online security measures and take appropriate actions to ensure that a competent review of the proposed security measures is conducted. As technology advances over time, a periodic review of the reasonability of security precautions may be necessary.