diff --git a/common/network/Blacklist.cxx b/common/network/Blacklist.cxx
new file mode 100644
index 0000000..a5caeea
--- /dev/null
+++ b/common/network/Blacklist.cxx
@@ -0,0 +1,61 @@
+/* Copyright (C) 2021 Kasm
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <netinet/tcp.h>
+#include <netdb.h>
+#include <time.h>
+
+#include <map>
+#include <string>
+
+#include <network/Blacklist.h>
+#include <rfb/Blacklist.h>
+
+static std::map<std::string, unsigned> hits;
+static std::map<std::string, time_t> blacklist;
+
+unsigned char bl_isBlacklisted(const char *addr) {
+	const unsigned char count = blacklist.count(addr);
+	if (!count)
+		return 0;
+
+	const time_t now = time(NULL);
+	const unsigned timeout = rfb::Blacklist::initialTimeout;
+
+	if (now - timeout > blacklist[addr]) {
+		blacklist.erase(addr);
+		hits.erase(addr);
+		return 0;
+	} else {
+		blacklist[addr] = now;
+		return 1;
+	}
+}
+
+void bl_addFailure(const char *addr) {
+	const unsigned num = ++hits[addr];
+	if (num >= (unsigned) rfb::Blacklist::threshold) {
+		blacklist[addr] = time(NULL);
+	}
+}
diff --git a/common/network/Blacklist.h b/common/network/Blacklist.h
new file mode 100644
index 0000000..799c796
--- /dev/null
+++ b/common/network/Blacklist.h
@@ -0,0 +1,33 @@
+/* Copyright (C) 2021 Kasm
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This software is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#ifndef __NETWORK_BLACKLIST_H__
+#define __NETWORK_BLACKLIST_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+unsigned char bl_isBlacklisted(const char *);
+void bl_addFailure(const char *);
+
+#ifdef __cplusplus
+} // extern C
+#endif
+
+#endif // __NETWORK_TCP_SOCKET_H__
diff --git a/common/network/CMakeLists.txt b/common/network/CMakeLists.txt
index d63c696..a767e73 100644
--- a/common/network/CMakeLists.txt
+++ b/common/network/CMakeLists.txt
@@ -2,6 +2,7 @@ include_directories(${CMAKE_SOURCE_DIR}/common ${CMAKE_SOURCE_DIR}/unix/kasmvncp
 
 set(NETWORK_SOURCES
   GetAPIMessager.cxx
+  Blacklist.cxx
   Socket.cxx
   TcpSocket.cxx
   websocket.c
diff --git a/common/network/websocket.c b/common/network/websocket.c
index 6270b49..01d246e 100644
--- a/common/network/websocket.c
+++ b/common/network/websocket.c
@@ -32,6 +32,7 @@
 #include <openssl/sha.h> /* sha1 hash */
 #include "websocket.h"
 #include "kasmpasswd.h"
+#include <network/Blacklist.h>
 
 /*
  * Global state
@@ -1203,7 +1204,7 @@ nope:
     return 1;
 }
 
-ws_ctx_t *do_handshake(int sock) {
+ws_ctx_t *do_handshake(int sock, const char *ip) {
     char handshake[4096], response[4096], sha1[29], trailer[17];
     char *scheme, *pre;
     headers_t *headers;
@@ -1271,10 +1272,20 @@ ws_ctx_t *do_handshake(int sock) {
         usleep(10);
     }
 
+    if (bl_isBlacklisted(ip)) {
+        wserr("IP %s is blacklisted, dropping\n", ip);
+        sprintf(response, "HTTP/1.1 401 Forbidden\r\n"
+                          "\r\n");
+        ws_send(ws_ctx, response, strlen(response));
+        free_ws_ctx(ws_ctx);
+        return NULL;
+    }
+
     unsigned char owner = 0;
     if (!settings.disablebasicauth) {
         const char *hdr = strstr(handshake, "Authorization: Basic ");
         if (!hdr) {
+            bl_addFailure(ip);
             handler_emsg("BasicAuth required, but client didn't send any. 401 Unauth\n");
             sprintf(response, "HTTP/1.1 401 Unauthorized\r\n"
                               "WWW-Authenticate: Basic realm=\"Websockify\"\r\n"
@@ -1288,6 +1299,7 @@ ws_ctx_t *do_handshake(int sock) {
         const char *end = strchr(hdr, '\r');
         if (!end || end - hdr > 256) {
             handler_emsg("Client sent invalid BasicAuth, dropping connection\n");
+            bl_addFailure(ip);
             free_ws_ctx(ws_ctx);
             return NULL;
         }
@@ -1357,6 +1369,7 @@ ws_ctx_t *do_handshake(int sock) {
 
         if (len <= 0 || strcmp(authbuf, response)) {
             handler_emsg("BasicAuth user/pw did not match\n");
+            bl_addFailure(ip);
             sprintf(response, "HTTP/1.1 401 Forbidden\r\n"
                               "\r\n");
             ws_send(ws_ctx, response, strlen(response));
@@ -1445,7 +1458,7 @@ void *subthread(void *ptr) {
 
     ws_ctx_t *ws_ctx;
 
-    ws_ctx = do_handshake(csock);
+    ws_ctx = do_handshake(csock, pass->ip);
     if (ws_ctx == NULL) {
         handler_msg("No connection after handshake\n");
         goto out;   // Child process exits