diff --git a/app/models/screened_ip_address.rb b/app/models/screened_ip_address.rb
index a4eb6e148f8..d5547660270 100644
--- a/app/models/screened_ip_address.rb
+++ b/app/models/screened_ip_address.rb
@@ -1,4 +1,5 @@
 require_dependency 'screening_model'
+require_dependency 'ip_addr'
 
 # A ScreenedIpAddress record represents an IP address or subnet that is being watched,
 # and possibly blocked from creating accounts.
@@ -47,18 +48,8 @@ class ScreenedIpAddress < ActiveRecord::Base
   end
 
   # Return a string with the ip address and mask in standard format. e.g., "127.0.0.0/8".
-  # Ruby's IPAddr class has no method for getting this.
   def ip_address_with_mask
-    if ip_address
-      mask = ip_address.instance_variable_get(:@mask_addr).to_s(2).count('1')
-      if mask == 32
-        ip_address.to_s
-      else
-        "#{ip_address}/#{ip_address.instance_variable_get(:@mask_addr).to_s(2).count('1')}"
-      end
-    else
-      nil
-    end
+    ip_address.try(:to_cidr_s)
   end
 
   def self.match_for_ip_address(ip_address)
diff --git a/app/services/user_destroyer.rb b/app/services/user_destroyer.rb
index def4bc3a919..4c0b34741c8 100644
--- a/app/services/user_destroyer.rb
+++ b/app/services/user_destroyer.rb
@@ -1,3 +1,5 @@
+require_dependency 'ip_addr'
+
 # Responsible for destroying a User record
 class UserDestroyer
 
@@ -45,16 +47,21 @@ class UserDestroyer
 
       user.destroy.tap do |u|
         if u
+
           if opts[:block_email]
             b = ScreenedEmail.block(u.email, ip_address: u.ip_address)
             b.record_match! if b
           end
+
           if opts[:block_ip] && u.ip_address
-            b.record_match! if b = ScreenedIpAddress.watch(u.ip_address)
+            b = ScreenedIpAddress.watch(u.ip_address)
+            b.record_match! if b
             if u.registration_ip_address && u.ip_address != u.registration_ip_address
-              b.record_match! if b = ScreenedIpAddress.watch(u.registration_ip_address)
+              b = ScreenedIpAddress.watch(u.registration_ip_address)
+              b.record_match! if b
             end
           end
+
           Post.with_deleted.where(user_id: user.id).update_all("user_id = NULL")
 
           # If this user created categories, fix those up:
diff --git a/lib/admin_user_index_query.rb b/lib/admin_user_index_query.rb
index c0e11cdc72a..17d07feb117 100644
--- a/lib/admin_user_index_query.rb
+++ b/lib/admin_user_index_query.rb
@@ -42,8 +42,8 @@ class AdminUserIndexQuery
 
   def filter_by_search
     if params[:filter].present?
-      if params[:filter] =~ Resolv::IPv4::Regex || params[:filter] =~ Resolv::IPv6::Regex
-        @query.where('ip_address = :ip OR registration_ip_address = :ip', ip: params[:filter])
+      if ip = IPAddr.new(params[:filter]) rescue nil
+        @query.where('ip_address <<= :ip OR registration_ip_address <<= :ip', ip: ip.to_cidr_s)
       else
         @query.where('username_lower ILIKE :filter OR email ILIKE :filter', filter: "%#{params[:filter]}%")
       end
diff --git a/lib/ip_addr.rb b/lib/ip_addr.rb
new file mode 100644
index 00000000000..c8afcde4807
--- /dev/null
+++ b/lib/ip_addr.rb
@@ -0,0 +1,16 @@
+class IPAddr
+
+  def to_cidr_s
+    if @addr
+      mask = @mask_addr.to_s(2).count('1')
+      if mask == 32
+        to_s
+      else
+        "#{to_s}/#{mask}"
+      end
+    else
+      nil
+    end
+  end
+
+end
diff --git a/lib/spam_handler.rb b/lib/spam_handler.rb
index 1df501babd1..6fc184e748d 100644
--- a/lib/spam_handler.rb
+++ b/lib/spam_handler.rb
@@ -4,21 +4,21 @@ class SpamHandler
     return false if SiteSetting.max_new_accounts_per_registration_ip <= 0
 
     tl2_plus_accounts_with_same_ip = User.where("trust_level >= ?", TrustLevel[2])
-                                         .where("ip_address = ?", ip_address.to_s)
+                                         .where(ip_address: ip_address.to_s)
                                          .count
 
     return false if tl2_plus_accounts_with_same_ip > 0
 
     staff_user_ids = Group[:staff].user_ids - [-1]
     staff_members_with_same_ip = User.where(id: staff_user_ids)
-                                     .where("ip_address = ?", ip_address.to_s)
+                                     .where(ip_address: ip_address.to_s)
                                      .count
 
     return false if staff_members_with_same_ip > 0
 
     tl0_accounts_with_same_ip = User.unscoped
                                     .where(trust_level: TrustLevel[0])
-                                    .where("ip_address = ?", ip_address.to_s)
+                                    .where(ip_address: ip_address.to_s)
                                     .count
 
     tl0_accounts_with_same_ip >= SiteSetting.max_new_accounts_per_registration_ip