Someone asked your computer "Are you there?". Your computer responded "Yes? What do you want?" and never heard from them again. Many times.
Probably not someone targetting you specifically, more likely a script kiddie (cyber vandal), who is using the computer that attacked yours (not likely its even their own) to attack random targets of opportunity.
I wouldn't worry about it unless I saw many of them from the same address range.
Aren't you glad you have a firewall? =)
http://docsrv.sco.com:507/en/NetAdminG/nwRs_SYNflood.htmlA ``SYN flood'' is a Denial of Service attack that takes advantage of the TCP ``three way handshake'' protocol. A SYN is a type of TCP packet sent to initiate a connection with a listening TCP port. The port responds with a SYN/ACK to the initiating port, and places the SYN packet in a partial connections queue. When a corresponding ACK packet is received on the listening port, the validated SYN packet is removed from the partial connections queue and an entry is placed in the established connection queue awaiting a socket connection.
A SYN flood occurs when one or more listening TCP ports are sent large numbers of SYN packets. Such attacks could take various forms, most of which do not adversely affect the attacked system. However, the most potentially harmful attack sends SYN packets in which the client address refers to a system which does not exist. In this case, SYN packets remain in the TCP partial connection queue for each listening port that is attacked, unable to complete because the SYN/ACK cannot be routed to a bogus address. If the queues are too small and packets awaiting response remain on the queues, the TCP stack refuses to accept any connections until the bogus packets have timed out.