diff --git a/service/proxy.go b/service/proxy.go
index 6cd96bb..23999fc 100644
--- a/service/proxy.go
+++ b/service/proxy.go
@@ -87,6 +87,11 @@ func handleRequest(w http.ResponseWriter, r *http.Request) {
 
 	site := getSiteByDomainWithWww(r.Host)
 	if site == nil {
+		if isHostIp(r.Host) {
+			w.WriteHeader(http.StatusBadRequest)
+			return
+		}
+
 		responseError(w, "CasWAF error: site not found for host: %s", r.Host)
 		return
 	}
diff --git a/service/util.go b/service/util.go
index 5e56db7..7ce5d96 100644
--- a/service/util.go
+++ b/service/util.go
@@ -17,6 +17,7 @@ package service
 import (
 	"crypto/tls"
 	"fmt"
+	"net"
 	"net/http"
 	"strings"
 
@@ -35,6 +36,12 @@ func joinPath(a string, b string) string {
 	return res
 }
 
+func isHostIp(host string) bool {
+	hostWithoutPort := strings.Split(host, ":")[0]
+	ip := net.ParseIP(hostWithoutPort)
+	return ip != nil
+}
+
 func responseOk(w http.ResponseWriter, format string, a ...interface{}) {
 	w.WriteHeader(http.StatusOK)