(Please trim inclusions from previous messages) _______________________________________________ You should check to make sure that you have the 'chargen' service disabled on your hosts, and block it in your routers if you can. I've already contacted the people whose system was involved in this attack. - Brian ----- Forwarded message ----- Subject: Exploitable chargen service used for an attack: 44.x.x.x. It appears that a public "chargen" service on your network, running on IP address 44.x.x.x, participated in a large-scale attack against a customer of ours today, generating large UDP responses to spoofed probes that claimed to be from the attack target. chargen is an old testing service that generates large quantities of traffic with only a small request required. It is commonly enabled by default on old printers and other connected appliances, but it has no useful purpose over the open internet. Please block UDP port 19 (inbound and outbound) at your network edge, as this should stop these chargen attacks without blocking legitimate traffic. If the endpoint device that generated this traffic is configurable, please further investigate whether it is running a chargen service (and disable it, if so) -- commonly exploited devices include Cisco hardware that has "udp small servers" mistakenly enabled, old printers, old UNIX boxes with "chargen" running under inetd, and Windows boxes with the "Simple TCP/IP services" package installed. Also, it is worth checking if it is a machine that has been compromised, as some malware directly generates port 19 traffic, simulating chargen, and in this way masks its presence. If you are an ISP, please also look at your network configuration and make sure that you do not allow spoofed traffic (that pretends to be from external IP addresses) to leave the network. Hosts that allow spoofed traffic make possible this type of attack. ----- End forwarded message ----- _________________________________________ 44Net mailing list 44Net(a)hamradio.ucsd.edu http://hamradio.ucsd.edu/mailman/listinfo/44net