Be sure your system is clean.
Set up a separate sandbox solely for banking and transactions.
Always flush the entire contents of that sandbox after session is completed so when use it again, it starts empty.Delete > Delete invocations > tick "automatically delete contents of sandbox"
Harden that sandbox by (a) making Google Chrome or(Other) the only program that can access the internet, (b) limiting what can start/run in that sandbox (in my case,Google Chrome), and (c) activating Drop Rights. These settings can be made via Sandboxie Control > Sandbox Settings > Restrictions. I also block access to My Documents (Sandboxie Control > Sandbox Settings > Resource Access > File Access).