A computer system is provided. The computer system includes a memory and at least one processor coupled to the memory and configured to recognize a user input field of a web site displayable in a browser, the website identified as a security risk based on a whitelist of website addresses; determine that a sequence of characters within the user input field matches one or more entries in a list of partial passwords in response to the web site being identified as a security risk; and prevent the user from entering additional characters into the user input field in response to the determination, to block receipt of the password by the web site. The determination may be performed in response to a count of characters in the sequence of characters exceeding a threshold.