I had noticed I had been getting these curious entries in my logfile on my linux box which is set up as a firewall. (I use Shorewall to manage IPTables) Feb 5 17:37:07 firewall kernel: Shorewall:all2all:REJECT:IN=eth1 OUT= MAC=00:a0:cc:3f:64:00:00:e0:7d:b8:78:72:08:00 SRC=192. 168.1.18 DST=192.168.1.1 LEN=160 TOS=0x00 PREC=0x00 TTL=128 ID=1638 PROTO=UDP SPT=1148 DPT=1900 LEN=140 Feb 5 17:42:04 firewall kernel: Shorewall:all2all:REJECT:IN=eth1 OUT= MAC=00:a0:cc:3f:64:00:00:02:e3:11:b7:cc:08:00 SRC=192. 168.1.4 DST=192.168.1.1 LEN=160 TOS=0x00 PREC=0x00 TTL=128 ID=5080 PROTO=UDP SPT=1211 DPT=1900 LEN=140 These happen to be Windows XP machines. The curious part is that I have properly disabled UPnP and SSDP Discovery on both system. With some investigating I managed to view the payload of the mysterious UDP packet. M-SEARCH * HTTP/1.1 HOST: 239.255.255.250:1900 MAN: "ssdp:discover" MX: 3 ST: urn:schemas-upnp-org:service:WANIPConnection:1 Anyway after even further investigation it seems that these mysterious packets are only sent if MSN messenger is launched. You don't even have to be logged into your MSN Messenger account. As long as it's sitting in your system tray, these packets seem to be sent every 10 to 15 seconds on machines with active MSN accounts and every 5 minutes or so on machines that haven't set up an MSN Messenger acount but still leave it sitting in the system tray. If anyone else can confirm this or know why MSN wants to talk like a UPnP device, I'd be appreciative to hear from you.
