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+---
+title: "Identity Verification Rate Limiting"
+description: "Rate limits in identity verification"
+layout: article
+category: AppDev
+subcategory: Architecture
+---
+
+This page lists the rate limits relating to identity verification, and provides details
+about each of them. 
+
+The following identity verification related rate limits exist:
+
+- [Hybrid Handoff](#hybrid-handoff-rate-limiter)
+- [Document Capture](#document-capture-rate-limiter)
+- [Verify Info](#verify-info-rate-limiter)
+- [Social Security Number](#social-security-number-rate-limiter)
+- [Phone Verification](#phone-verification-rate-limiter)
+- [One time code entry](#one-time-code-entry-rate-limiter)
+- [Verify by USPS mail](#verify-by-usps-mail-rate-limiter)
+
+In the past, only failed attempts at each step counted against
+rate limiting. We are now counting successful attempts as well,
+except for the OTP code, which still only counts failures.
+
+# Rate Limit Details
+## Hybrid Handoff rate limiter
+### Description
+This is the rate limiter for sending a link from Hybrid Handoff to
+enter the hybrid mobile flow, where we allow the user to upload their
+ID documents from their phone. It is referred to in code via
+`:idv_send_link` and the `RateLimiter` class.
+
+By default, the user is allowed 5 attempts in 10 minutes.
+
+### Settings
+`idv_send_link_max_attempts` - The maximum number of times that a user
+can attempt to upload their ID documents from their phone within the
+specified time window. Default: 5 attempts
+
+`idv_send_link_attempt_window_in_minutes` - The length of time to
+consider when determining whether a user is rate limited. Default: 10
+minutes
+
+### How to trigger
+On the Hybrid Handoff step, select `Send link`. Click the `Back` link
+at the bottom of the next screen (Link Sent) and return to the
+previous page. Click `Send link` again. Repeat until you become rate
+limited.
+### UI effects
+The user will be presented with a flash error message every time they
+attempt to enter Hybrid Handoff.
+
+![Rate Limited Hybrid Handoff]({{site.baseurl}}/images/hybrid-handoff-limited.png)
+
+## Document Capture rate limiter
+### Description
+This is the rate limit for the user's attempts to upload their ID
+documents from either their computer or phone. It is referred to in
+code via `:idv_doc_auth` and the `RateLimiter` class.
+
+All document submissions, whether successful or not, count against
+this rate limit. The user gets 5 attempts in 6 hours total, through
+any path.
+
+### Config Settings
+- `doc_auth_max_attempts` - The maximum number of times the user can
+  attempt to upload their documents within the specified time
+  window. Default: 5 tries
+
+- `doc_auth_attempts_window_in_minutes` - The length of time to
+  consider when determining whether a user is rate limited. Default: 6
+  hours.
+
+### How to trigger
+The quickest way to test this is to fail repeatedly.
+
+### How to make this step fail
+This can be done by using a suitable `.yml` file rather than an image
+file during image upload.
+
+Use the same file for front and back images, but you must alternate
+between two files on successive attempts. The UI will not let you try
+twice in a row with the same file.
+
+A pair of suitable files to fail doc auth is:
+
+```
+image_metrics:
+  back:
+    HorizontalResolution: 100
+```
+
+```
+failed_alerts:
+  - name: Document Classification
+    result: Attention
+```
+
+[More about Yaml files for testing and development](https://developers.login.gov/testing/#testing-identity-proofing)
+
+
+### UI effects
+
+After failing for the final time, the user will be redirected to a
+rate limited screen. Any attempt to re-enter identity verification will also
+redirect there.
+
+![Failed and Rate Limited]({{site.baseurl}}/images/idv-doc-auth-limited.png)
+
+## Verify Info rate limiter
+### Description
+This is the rate limit for verifying the user's information against
+our external vendors. It is referred to in code via `:idv_resolution`
+and the `RateLimiter` class.
+
+By default, the user is allowed 5 attempts in 6 hours.
+
+### Config Settings
+- `idv_max_attempts` - The maximum number of times the user can verify
+  their information within the specified time window. Default: 5 tries
+
+- `idv_attempt_window_in_hours` - The length of time to consider when
+  determining whether a user is rate limited. Default: 6 hours.
+
+### How to trigger
+The quickest way to test this is to fail repeatedly.
+
+### How to make this step fail
+Submit Verify Info with an SSN that does not begin with 900 or 666;
+it will fail. On the warning screen, click `Try again`, and repeat.
+
+### UI effects
+After failing for the final time, the user will be redirected to a
+rate limited screen. Any attempt to re-enter identity verification will also
+redirect there.
+
+![Failed and Rate Limited]({{site.baseurl}}/images/verify-info-rate-limited.png)
+
+## Social Security number rate limiter
+### Description
+This is a rate limiter specifically to prevent multiple users from
+using the same SSN. It is referred to in code via `:proof_ssn` and the
+`RateLimiter` class.
+
+By default, an SSN is allowed 10 attempts in 60 minutes, across any
+number of users. The discriminator for this rate limiter is the SSN,
+not the user id.
+
+### Settings
+- `proof_ssn_max_attempts` - The maximum number of times that a Social
+Security number can be part of a verification attempt within the
+specified window. Default: 10 attempts.
+
+- `proof_ssn_max_attempt_window_in_minutes` - The length of time to
+consider when determining whether a Social Security number is
+rate-limited. Default: 60 minutes.
+
+### How to trigger
+The quickest way to test this is to fail repeatedly.
+
+This rate limiter is checked at the Verify Info step. The limit for it
+is set to double the resolution rate limiter, so it takes three users
+with a common SSN to trigger the SSN rate limit.
+
+### How to make this step fail
+Choose an SSN that does not begin with 900 or 666.  Create
+a new user, and attempt identity verification with the user. The
+Verify Info step will fail with this SSN. Repeat until rate limited.
+At this point, you are rate limited by the resolution rate limiter,
+not the SSN rate limiter.
+
+Create a second user, and repeat the process with the same SSN.
+
+Create a third user. Repeat with the same SSN, and this time, you will see
+the SSN rate limit page after submitting the Verify Info step.
+
+The SSN rate limit error page can be distinguished from the resolution
+rate limit error page by the fact that the SSN timeout is 1 hour,
+whereas the resolution limiter has a timeout of 6 hours.
+
+## Phone Verification rate limiter
+### Description
+This is the rate limiter for the Phone verification step, which
+confirms that the user is reachable at a verified phone number or
+address. It is referred to in code via `:proof_address` and the
+`RateLimiter` class.
+
+By default, the user is allowed 5 attempts in 6 hours.
+
+### Config Settings
+- `proof_address_max_attempts` - The maximum number of times that a
+user can attempt to verify their address within the specified
+window. Default: 5 attempts.
+
+- `proof_address_max_attempt_window_in_minutes` - The length of time
+to consider when determining whether a user is rate limited. Default:
+6 hours
+
+### How to trigger
+The quickest way to test this is to fail repeatedly.
+
+### How to make this step fail
+Use phone number 703-555-5555. The phone step will fail. Retry,
+using the same phone number, until you are rate limited. Ignore the
+message about using a different phone number.
+
+### UI effects
+
+The user will be redirected to a screen informing them that they are
+rate-limited and give them the option of verifying by mail instead.
+
+If Verify by Mail is available to them, they will be able to re-start
+identity verification and will see this screen when they reach the
+Phone step.
+
+If Verify by Mail is unavailable or they are also rate-limited for
+sending letters, they will see this screen when starting Identity
+Verification.
+
+![Proof Address Rate Limited]({{site.baseurl}}/images/idv-proof-address-rate-limited.png)
+
+## One time code entry rate limiter
+### Description
+During the phone confirmation step, the user must enter a one-time
+code sent to their phone. This is the rate limiter for requesting
+one-time codes.
+
+When the user is entering a one-time code, rate limiting is
+handled by code which is common to both OTP entry during
+identity verification _and_ during user login.
+
+The actual rate limit count is stored on the `User` class. Most of the
+code is in the `UserOtpMethods` concern, with a small bit of it still
+in `User`.
+
+By default, the user is allowed to request 10 one-time codes
+within 10 minutes.
+
+If the user requests more than 10, they are blocked from further
+access, and must wait 10 minutes before being allowed to continue.
+
+### Settings
+`:login_otp_confirmation_max_attempts` - The maximum number of OTP
+ entry attempts that the user is allowed before their account is
+ temporarily locked. Default: 10 tries.
+
+`:lockout_period_in_minutes` - The length of time that a use must wait
+after being locked out for too many OTP requests before they are
+allowed to try again. Default: 10 minutes.
+
+### How to trigger
+Enter identity verification and proceed through the 'Verify your phone
+number' screen. After pressing the 'Send code' button, you will be on
+the 'Enter your one-time code' screen. Press the 'Send another code
+button' repeatedly, until you are rate limited.
+
+### UI effects
+On any attempt to access Identity Verification, the user will be redirected to a
+rate-limited page, until the rate limit expires. They can access the account page, 
+but cannot log in after logging out.
+
+![Rate Limited]({{site.baseurl}}/images/otp-limited.png)
+## Verify by USPS mail rate limiter
+### Description
+This is the rate limiter for a user's requests for USPS paper (also
+sometimes called GPO) letters.  This is a completely independent set
+of rate limiting code in the `GpoMail` class, which implements two
+rate limits.
+
+- First, a user is not allowed more than a certain number of letter
+  requests within a time window (this is similar to the other rate
+  limiters described here).
+
+- Second, there is a minimum wait period after requesting a letter
+  before a user is allowed to request another.
+
+  By default, a user is allowed to request 4 verify by mail letters
+  within 30 days, and must wait 24 hours after requesting a letter
+  before they are allowed to request another. 
+
+  (n.b. - there is an override for this in `application.yml` if the
+  RUBY_ENV environment variable is set to `test`. In that case, users
+  are restricted to 2 letters per 30 day window; the delay is still 24
+  hours. This setting is used by the automated test suite in CI and
+  also for local development. It makes the tests simpler to have a
+  lower rate limiting threshold.)
+
+### Settings
+`max_mail_events` - The maximum number of times that a user may
+request a Verify by Mail letter within the specified time window. Default: 4 requests.
+
+`max_mail_events_window_in_days` - The length of time to consider when
+determining whether the user has requested too many Verify by Mail letters
+recently. Default: 30 days.
+
+`minimum_wait_before_another_usps_letter_in_hours` - The minimum
+amount of time that a user must wait, after requesting a Verify by Mail letter,
+before requesting another letter. Default: 24 hours.
+
+### How to trigger
+Enter identity verification and select "Verify by Mail". Request a
+letter; you are now rate limited.
+
+### UI effects
+On the screen to enter their verification code, the user is not
+presented with the option to request another letter, and they are
+shown a warning banner explaining why.
+
+[Rate limited]({{site.baseurl}}/images/gpo_letter_request_rate_limited.png)
+
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