diff --git a/SS14.Auth.Shared/ModelShared.cs b/SS14.Auth.Shared/ModelShared.cs
index 155367e..f16233a 100644
--- a/SS14.Auth.Shared/ModelShared.cs
+++ b/SS14.Auth.Shared/ModelShared.cs
@@ -1,6 +1,6 @@
+using System;
 using System.Text.Encodings.Web;
 using System.Threading.Tasks;
-using Microsoft.AspNetCore.Authentication;
 using SS14.Auth.Shared.Data;
 using SS14.Auth.Shared.Emails;
 
@@ -15,6 +15,17 @@ await sender.SendEmailAsync(address, "Confirm your Space Station 14 account",
             $"\n<p><small>If the above link is not working, try this one {HtmlEncoder.Default.Encode(confirmLink)}</small></p>");
     }
 
+    public static async Task SendAccountExistsEmail(IEmailSender sender, string address, string loginUrl)
+    {
+        await sender.SendEmailAsync(address, "Registration attempt on your Space Station 14 account",
+            "Someone just tried to register a new Space Station 14 account using this email address, " +
+            "but an account already exists for it. No new account was created.<br />" +
+            $"\n<p>If this was you: you already have an account - just <a href='{loginUrl}'>log in</a>, " +
+            "or reset your password from the login page if you've forgotten it.</p>" +
+            "\n<p>If this wasn't you, you don't need to do anything. Your account is unaffected.</p>" +
+            $"\n<p><small>If the link above is not working, go to {HtmlEncoder.Default.Encode(loginUrl)}</small></p>");
+    }
+
     public static async Task SendResetEmail(IEmailSender emailSender, string email, string callbackUrl)
     {
         await emailSender.SendEmailAsync(
@@ -22,11 +33,11 @@ await emailSender.SendEmailAsync(
             "A password reset has been requested for your account.<br />" +
             $"If you did indeed request this, <a href='{callbackUrl}'>click here</a> to reset your password.<br />" +
             "If you did not request this, simply ignore this email." +
-            $"\n<p><small>If the above link is not working, try this one {HtmlEncoder.Default.Encode(callbackUrl)}</small></p");
+            $"\n<p><small>If the above link is not working, try this one {HtmlEncoder.Default.Encode(callbackUrl)}</small></p>");
     }
 
-    public static SpaceUser CreateNewUser(string userName, string email, ISystemClock systemClock)
+    public static SpaceUser CreateNewUser(string userName, string email, DateTimeOffset timeOffset)
     {
-        return new SpaceUser {UserName = userName, Email = email, CreatedTime = systemClock.UtcNow};
+        return new SpaceUser { UserName = userName, Email = email, CreatedTime = timeOffset };
     }
 }
diff --git a/SS14.Auth/Controllers/AuthApiController.cs b/SS14.Auth/Controllers/AuthApiController.cs
index f079d39..4ff9122 100644
--- a/SS14.Auth/Controllers/AuthApiController.cs
+++ b/SS14.Auth/Controllers/AuthApiController.cs
@@ -1,19 +1,20 @@
-using System;
-using System.Diagnostics;
-using System.Linq;
-using System.Text;
-using System.Text.Json.Serialization;
-using System.Threading.Tasks;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.AspNetCore.WebUtilities;
 using Microsoft.Extensions.Configuration;
-using Microsoft.Extensions.Internal;
 using SS14.Auth.Shared;
 using SS14.Auth.Shared.Data;
 using SS14.Auth.Shared.Emails;
 using SS14.Auth.Shared.Sessions;
+using System;
+using System.ComponentModel.DataAnnotations;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Text.Json.Serialization;
+using System.Threading.Tasks;
 
 namespace SS14.Auth.Controllers;
 
@@ -26,16 +27,25 @@ public class AuthApiController : ControllerBase
 {
     private readonly SessionManager _sessionManager;
     private readonly IEmailSender _emailSender;
-    private readonly ISystemClock _systemClock;
+    private readonly TimeProvider _systemClock;
     private readonly IConfiguration _cfg;
 
     private readonly SpaceUserManager _userManager;
     private readonly SignInManager<SpaceUser> _signInManager;
 
+    private readonly Lazy<SpaceUser> _dummyUser = new(() =>
+    {
+        var u = new SpaceUser();
+        u.PasswordHash = new PasswordHasher<SpaceUser>().HashPassword(u, "timing-equalizer");
+        return u;
+    });
+
     private string WebBaseUrl => _cfg.GetValue<string>("WebBaseUrl") ?? "";
 
+    private const string DuplicateEmailCode = "DuplicateEmail";
+
     public AuthApiController(SpaceUserManager userManager, SignInManager<SpaceUser> signInManager,
-        SessionManager sessionManager, IEmailSender emailSender, ISystemClock systemClock, IConfiguration cfg)
+        SessionManager sessionManager, IEmailSender emailSender, TimeProvider systemClock, IConfiguration cfg)
     {
         _userManager = userManager;
         _signInManager = signInManager;
@@ -45,17 +55,17 @@ public AuthApiController(SpaceUserManager userManager, SignInManager<SpaceUser>
         _cfg = cfg;
     }
 
+    [EnableRateLimiting("authenticate")]
     [HttpPost("authenticate")]
     public async Task<IActionResult> Authenticate(AuthenticateRequest request)
     {
         // Password may never be null, and only either username OR userID can be used for login, not both.
         if (!(request.Username == null ^ request.UserId == null))
-        {
-            return BadRequest();
-        }
-
-        // Console.WriteLine(Request.Headers["SS14-Launcher-Fingerprint"]);
-        // Console.WriteLine(Request.Headers["User-Agent"]);
+            return BadRequest(new
+            {
+                Error = "invalid_request",
+                Message = "Exactly one of Username or UserId must be provided."
+            });
 
         SpaceUser? user;
         if (request.Username != null)
@@ -65,12 +75,13 @@ public async Task<IActionResult> Authenticate(AuthenticateRequest request)
         else
         {
             Debug.Assert(request.UserId != null);
-
             user = await _userManager.FindByIdAsync(request.UserId!.Value.ToString());
         }
 
         if (user == null)
         {
+            await _signInManager.CheckPasswordSignInAsync(_dummyUser.Value, request.Password, false);
+
             return Unauthorized(new AuthenticateDenyResponse(
                 new[] { "Invalid login credentials." },
                 AuthenticateDenyResponseCode.InvalidCredentials));
@@ -113,42 +124,57 @@ public async Task<IActionResult> Authenticate(AuthenticateRequest request)
                     new[] { "" },
                     AuthenticateDenyResponseCode.TfaRequired));
             }
-            
+
             var verify = await _userManager.VerifyTwoFactorTokenAsync(
                 user, 
                 _userManager.Options.Tokens.AuthenticatorTokenProvider,
                 request.TfaCode);
-            
+
             if (!verify)
             {
                 return Unauthorized(new AuthenticateDenyResponse(
                     new[] { "" },
                     AuthenticateDenyResponseCode.TfaInvalid));
             }
-            
+
             // 2FA passed, we're good.
         }
-        
+
         var (token, expireTime) =
             await _sessionManager.RegisterNewSession(user, SessionManager.DefaultExpireTime);
 
         return Ok(new AuthenticateResponse(token.AsBase64, user.UserName!, user.Id, expireTime));
     }
 
-    // Launcher registration disabled due to spam risk.
-    /*
+    [EnableRateLimiting("registration")]
     [HttpPost("register")]
     public async Task<IActionResult> Register(RegisterRequest request)
     {
         var userName = request.Username.Trim();
         var email = request.Email.Trim();
 
-        var user = ModelShared.CreateNewUser(userName, email, _systemClock);
+        var user = ModelShared.CreateNewUser(userName, email, _systemClock.GetUtcNow());
         var result = await _userManager.CreateAsync(user, request.Password);
 
+        var successStatus = _userManager.Options.SignIn.RequireConfirmedEmail
+            ? RegisterResponseStatus.RegisteredNeedConfirmation
+            : RegisterResponseStatus.Registered;
+
         if (!result.Succeeded)
         {
-            var errors = result.Errors.Select(p => p.Description).ToArray();
+            var errors = result.Errors
+                .Where(e => e.Code != DuplicateEmailCode)
+                .Select(e => e.Description)
+                .ToArray();
+
+            if (errors.Length == 0)
+            {
+                var loginUrl = $"{WebBaseUrl}Identity/Account/Login";
+                await ModelShared.SendAccountExistsEmail(_emailSender, email, loginUrl);
+
+                return Ok(new RegisterResponse(successStatus));
+            }
+
             return UnprocessableEntity(new RegisterResponseError(errors));
         }
 
@@ -156,14 +182,10 @@ public async Task<IActionResult> Register(RegisterRequest request)
 
         await ModelShared.SendConfirmEmail(_emailSender, email, confirmLink);
 
-        var status = _userManager.Options.SignIn.RequireConfirmedAccount
-            ? RegisterResponseStatus.RegisteredNeedConfirmation
-            : RegisterResponseStatus.Registered;
-
-        return Ok(new RegisterResponse(status));
+        return Ok(new RegisterResponse(successStatus));
     }
-    */
 
+    [EnableRateLimiting("reset-password")]
     [HttpPost("resetPassword")]
     public async Task<IActionResult> ResetPassword(ResetPasswordRequest request)
     {
@@ -185,8 +207,7 @@ public async Task<IActionResult> ResetPassword(ResetPasswordRequest request)
         return Ok();
     }
 
-    // Launcher resend confirmation disabled due to spam risk.
-    /*
+    [EnableRateLimiting("resend-confirmation")]
     [HttpPost("resendConfirmation")]
     public async Task<IActionResult> ResendConfirmation(ResendConfirmationRequest request)
     {
@@ -194,18 +215,14 @@ public async Task<IActionResult> ResendConfirmation(ResendConfirmationRequest re
 
         var user = await _userManager.FindByEmailAsync(email);
 
-        if (user == null)
+        if (user != null && !await _userManager.IsEmailConfirmedAsync(user))
         {
-            return Ok();
+            var confirmLink = await GenerateEmailConfirmLink(user);
+            await ModelShared.SendConfirmEmail(_emailSender, email, confirmLink);
         }
 
-        var confirmLink = await GenerateEmailConfirmLink(user);
-
-        await ModelShared.SendConfirmEmail(_emailSender, email, confirmLink);
-
         return Ok();
     }
-    */
 
     [Authorize(AuthenticationSchemes = "SS14Auth")]
     [HttpGet("ping")]
@@ -281,40 +298,27 @@ public enum AuthenticateDenyResponseCode
     // @formatter:on
 }
 
-public sealed record RegisterRequest(string Username, string Email, string Password)
-{
-}
+public sealed record RegisterRequest(
+    [Required, StringLength(32, MinimumLength = 3)] string Username,
+    [Required, EmailAddress] string Email,
+    [Required, StringLength(100, MinimumLength = 6)] string Password);
 
-public sealed record ResetPasswordRequest(string Email)
-{
-}
+public sealed record ResetPasswordRequest([Required, EmailAddress] string Email);
 
-public sealed record ResendConfirmationRequest(string Email)
-{
-}
+public sealed record ResendConfirmationRequest([Required, EmailAddress] string Email);
 
-public sealed record RegisterResponse(RegisterResponseStatus Status)
-{
-}
+public sealed record RegisterResponse(RegisterResponseStatus Status);
 
-public sealed record RegisterResponseError(string[] Errors)
-{
-}
+public sealed record RegisterResponseError(string[] Errors);
 
-public sealed record LogoutRequest(string Token)
-{
-}
+public sealed record LogoutRequest(string Token);
 
-public sealed record RefreshRequest(string Token)
-{
-}
+public sealed record RefreshRequest(string Token);
 
-public sealed record RefreshResponse(DateTimeOffset ExpireTime, string NewToken)
-{
-}
+public sealed record RefreshResponse(DateTimeOffset ExpireTime, string NewToken);
 
 public enum RegisterResponseStatus
 {
     Registered,
     RegisteredNeedConfirmation
-}
\ No newline at end of file
+}
diff --git a/SS14.Auth/Startup.cs b/SS14.Auth/Startup.cs
index 817196e..1a03b9b 100644
--- a/SS14.Auth/Startup.cs
+++ b/SS14.Auth/Startup.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -11,6 +12,8 @@
 using SS14.Auth.Shared;
 using SS14.Auth.Shared.Auth;
 using SS14.WebEverythingShared;
+using System;
+using System.Threading.RateLimiting;
 
 namespace SS14.Auth;
 
@@ -36,6 +39,61 @@ public void ConfigureServices(IServiceCollection services)
                 .Build());
         });
 
+        services.AddRateLimiter(options =>
+        {
+            options.AddPolicy("registration", httpContext =>
+            {
+                var ip = httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+                return RateLimitPartition.GetFixedWindowLimiter(ip, _ =>
+                    new FixedWindowRateLimiterOptions
+                    {
+                        PermitLimit = 5,
+                        Window = TimeSpan.FromMinutes(15),
+                        QueueLimit = 0,
+                    });
+            });
+
+            options.AddPolicy("resend-confirmation", httpContext =>
+            {
+                var ip = httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+                return RateLimitPartition.GetFixedWindowLimiter(ip, _ =>
+                    new FixedWindowRateLimiterOptions
+                    {
+                        PermitLimit = 2,
+                        Window = TimeSpan.FromHours(1),
+                        QueueLimit = 0,
+                    });
+            });
+
+            options.AddPolicy("authenticate", httpContext => {
+                var ip = httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+                return RateLimitPartition.GetFixedWindowLimiter(ip, _ =>
+                    new FixedWindowRateLimiterOptions
+                    {
+                        PermitLimit = 10,
+                        Window = TimeSpan.FromMinutes(1),
+                        QueueLimit = 0
+                    });
+            });
+
+            options.AddPolicy("reset-password", httpContext => {
+                var ip = httpContext.Connection.RemoteIpAddress?.ToString() ?? "unknown";
+                return RateLimitPartition.GetFixedWindowLimiter(ip, _ =>
+                    new FixedWindowRateLimiterOptions
+                    {
+                        PermitLimit = 3,
+                        Window = TimeSpan.FromMinutes(15),
+                        QueueLimit = 0
+                    });
+            });
+
+            options.OnRejected = async (ctx, token) =>
+            {
+                ctx.HttpContext.Response.StatusCode = StatusCodes.Status429TooManyRequests;
+                await ctx.HttpContext.Response.WriteAsJsonAsync(new { Error = "rate_limited" }, token);
+            };
+        });
+
         services.AddAuthentication()
             .AddScheme<SS14AuthOptions, SS14AuthHandler>("SS14Auth", _ => {});
 
@@ -85,6 +143,8 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
 
         app.UseRouting();
 
+        app.UseRateLimiter();
+
         app.UseHttpMetrics();
         
         app.UseAuthorization();
@@ -95,4 +155,4 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
             endpoints.MapMetrics();
         });
     }
-}
\ No newline at end of file
+}
diff --git a/SS14.Web/Areas/Admin/Pages/Users/CreateReserved.cshtml.cs b/SS14.Web/Areas/Admin/Pages/Users/CreateReserved.cshtml.cs
index 37e35cc..5a9f12f 100644
--- a/SS14.Web/Areas/Admin/Pages/Users/CreateReserved.cshtml.cs
+++ b/SS14.Web/Areas/Admin/Pages/Users/CreateReserved.cshtml.cs
@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Buffers.Text;
 using System.ComponentModel.DataAnnotations;
 using System.Security.Cryptography;
@@ -47,7 +47,7 @@ public async Task<IActionResult> OnPostAsync()
 
         var password = Convert.ToHexString(RandomNumberGenerator.GetBytes(32));
 
-        var user = ModelShared.CreateNewUser(userName, $"reserved+{userName}@playss14.com", _systemClock);
+        var user = ModelShared.CreateNewUser(userName, $"reserved+{userName}@playss14.com", _systemClock.UtcNow);
         user.AdminLocked = true;
         user.AdminNotes = "Account reserved via admin panel. If unlocking, change email and password!";
         user.EmailConfirmed = true;
diff --git a/SS14.Web/Areas/Identity/Pages/Account/Register.cshtml.cs b/SS14.Web/Areas/Identity/Pages/Account/Register.cshtml.cs
index bfe5e2f..20cbcbd 100644
--- a/SS14.Web/Areas/Identity/Pages/Account/Register.cshtml.cs
+++ b/SS14.Web/Areas/Identity/Pages/Account/Register.cshtml.cs
@@ -56,6 +56,7 @@ public RegisterModel(
     public class InputModel
     {
         [Required]
+        [StringLength(32, ErrorMessage = "The {0} must be at least {2} and at max {1} characters long.", MinimumLength = 3)]
         [Display(Name = "Username")]
         public string Username { get; set; }
 
@@ -101,7 +102,7 @@ public async Task<IActionResult> OnPostAsync(string returnUrl = null)
         if (!await _hCaptcha.ValidateHCaptcha(HCaptchaResponse, ModelState))
             return Page();
 
-        var user = ModelShared.CreateNewUser(userName, email, _systemClock);
+        var user = ModelShared.CreateNewUser(userName, email, _systemClock.UtcNow);
         var result = await _userManager.CreateAsync(user, Input.Password);
         if (result.Succeeded)
         {
@@ -150,4 +151,4 @@ public async Task<string> GenerateEmailConfirmLink(
             protocol: Request.Scheme);
         return callbackUrl;
     }
-}
\ No newline at end of file
+}