In addition to each of these deal breakers: Designers rarely consider adding MFA steps for account information changes - leaving you unprotected when your valid session token is compromised.Smartphone malware is capable of intercepting and relaying text messages, and many devices run outdated versions of Android.Senders rarely verify if the number is associated with any Telco provider and not some VoIP service that does not establish possession of something you have.Secrets are sent across a public mobile telephone network - which is far from secure! (due to SS7 protocol vulnerabilities).However, if used for anything other than alerting you of important account activity, dangerous for several reasons: Why is Out-of-Band Authentication bad practice?Ĭonceptually sending an email or text is another sound strategy that provides a good user experience. Phishing the rest is made easy if usernames are email addresses. Given time, between the lists of commonly used passwords and their human-preferred permutations, an attacker can expect to recover passwords for ~20% of users. Showing a different error message depending on if the user exists or whether it was an invalid password is a dead giveaway.Įven when the login process is designed with care, mobile APIs, registration forms, username/password recovery and change features are seldom fitted with the same protections. Thankfully, fewer developers give away even easier clues in error messages these days. The extra database lookups and hashing make it apparent.Įven if the attacker has no success enumerating valid usernames via timing attacks, often subtle changes in the HTML body, HTTP response headers or the way Cookies are handled still give it away. Though this may appear to be a sound strategy, it allows an attacker to enumerate valid/invalid usernames based on the time it takes to get a response. Whenever you log in, oftentimes an app checks your username first, if it finds a match, it will take the computational effort to hash the password, and compare it against the hash value stored in its database. An attacker with no prior knowledge can learn a lot by how a web application or service responds to his requests. Most security controls do not detect let alone block attacks against web applications and web browsers. We forget that discovering valid usernames is half the battle for cyber criminals, why make it easy?ĭiscovering valid usernames is half the battle for an attacker aided by large public datasets from past data breaches - or predictable (corporate) email address patterns, coupled with names harvested from LinkedIn. The combination of a username (often your email address) and password are regularly the sole means of authenticating your identity as a valid user - which in term dictates what you are authorized to do.
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