When filtering traffic to localhost (127.0.0.1), it causes Maven repository synchronization to fail in IntelliJ IDEA. However, Maven works correctly when local traffic is not filtered. I will provide a minimal code reproduction below. - (void)startFilterWithCompletionHandler:(void (^)(NSError *error))completionHandler { // Add code to initialize the filter NSMutableArray *rules = [NSMutableArray array]; NENetworkRule * rule = [[NENetworkRule alloc] initWithRemoteNetwork:nil remotePrefix:0 localNetwork:nil localPrefix:0 protocol:NENetworkRuleProtocolTCP direction:NETrafficDirectionAny]; [rules addObject:[[NEFilterRule alloc]initWithNetworkRule:rule action:NEFilterActionFilterData]]; rule = [[NENetworkRule alloc] initWithRemoteNetwork:nil remotePrefix:0 localNetwork:nil localPrefix:0 protocol:NENetworkRuleProtocolUDP direction:NETrafficDirectionAny]; [rules addObject:[[NEFilterRule alloc]initWithNetworkRule:rule action:NEFilterActionFilterData]]; NWHostEndpoint *hostEndpointIpv4 = [NWHostEndpoint endpointWithHostname:@"127.0.0.1" port:@"0"]; NENetworkRule *localHostRuleIpv4 = [[NENetworkRule alloc] initWithRemoteNetwork:hostEndpointIpv4 remotePrefix:32 localNetwork:hostEndpointIpv4 localPrefix:32 protocol:NENetworkRuleProtocolAny direction:NETrafficDirectionAny]; [rules addObject:[[NEFilterRule alloc]initWithNetworkRule:localHostRuleIpv4 action:NEFilterActionFilterData]]; NEFilterSettings *filterSetting = [[NEFilterSettings alloc] initWithRules:rules defaultAction:NEFilterActionAllow]; [self applySettings:filterSetting completionHandler:^(NSError * _Nullable error) { if (error) { NSLog(@"Failed to apply filter settring: %@", error.localizedDescription); } completionHandler(error); }]; } Maven Sync error: System Log: 默认 17:35:13.184509+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so 3bb6402f58a82e37 - flags 0x800840 0x80> lport 63166 fport 29735 laddr 127.0.0.1 faddr 127.0.0.1 默认 17:35:13.184510+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so d6dde374c8cb613b - flags 0x800840 0x80> lport 63165 fport 29735 laddr 127.0.0.1 faddr 127.0.0.1 默认 17:35:13.529546+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so cc915e74ba29f8cb - flags 0x800840 0x80> lport 63169 fport 39066 laddr 127.0.0.1 faddr 127.0.0.1 默认 17:35:13.529546+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so 2e15c3e54ebcc45 - flags 0x800840 0x80> lport 63168 fport 39066 laddr 127.0.0.1 faddr 127.0.0.1 默认 17:35:14.046094+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so 71f6d3a53472131f - flags 0x800840 0x80> lport 63172 fport 53241 laddr 127.0.0.1 faddr 127.0.0.1 默认 17:35:14.046145+0800 kernel cfil_inp_log:6179 <CFIL: outbound TCP data dropped for pre-existing un-filtered flow>: [41046 idea] <TCP out so c88a367c9717185b - flags 0x800840 0x80> lport 63171 fport 53241 laddr 127.0.0.1 faddr 127.0.0.1 Environment Details: Operating System: macOS 15.5 (Sequoia) IDE: IntelliJ IDEA 2025.1 Relevant Technology: NEFilterDataProvider (Network Extension) I have found reports of similar problems online： https://discussionschinese.apple.com/thread/255270330?sortBy=rank https://blog.csdn.net/weixin_42339552/article/details/137402307 They all seem to be caused by network extension。