In August 2011, the American Bar Association Standing Committee on Ethics and Professional Responsibility issued Formal Opinion 11 - 459 relating to a lawyer's duty to protect the confidentiality of electronic communications with clients. (lawyerist.com)
(You can see the list of states that have offered formal opinions on the American Bar Association's website.) (clio.com)
Also, your ethical rules and opinions (e.g. ABA Formal Opinion No. 99 - 414) may give direct guidance as to what steps must be taken. (2civility.org)