How secure are online financial portals? Is it safe to transmit my financial information over a lending portal, and what security protocols do they have on the back end to guard against identity theft?
Brutus has a good answer, but you may also want to check with your financial institution and ask them directly. That will give you the most up to date and complete information about how they handle transactions in terms of security.
There are US Government standards for what financial institutions must do on the backend. While much of this is intended to fight crime, there are consumer protections as well. FFEIC provides guidance as to what financial institutions should do to meet applicable standards of identification and authentication. This applies even if the financial institution is relying on a 3rd party, such as a cloud services provider. The institution must ensure the provider meets applicable standards.
In addition, step one of any sensitive transaction online is to ensure that there is secure communication between yourself and your bank. Look for a HTTPS connection, which will minimize the risk of MITM attacks through bidirectional encryption.