Spam
Undesirable email message, usually containing advertisments.
Spoofing
Spoofing means using false IP addresses in packets. This method is used by at- tackers to make recipients assume that the packet is coming from a trustworthy IP address.
SSL
SSL is a protocol used to secure and encrypt network communication. SSL was originally designed by Netscape in order to ensure secure transfer of Web pages over HTTP protocol. Nowadays, it is used by most standard Internet protocols (SMTP, POP3, IMAP, LDAP, etc.).
At the beginning of communication, an encryption key is requested and transferred using asymmetrical encryption. This key is then used to encrypt (symmetrically) the data.
Subnet mask
Subnet mask divides an IP address in two parts: network mask and an ad- dress of a host in the network. Mask have the same form as IP addresses (i.e. 255.255.255.0), however, its value is needed to be understood as a
TCP
Transmission Control Protocol is a transmission protocol which ensures reliable and sequentional data delivery. It establishes so called virtual connections and provides tools for error correction and data stream control. It is used by most of applications protocols which require reliable transmission of all data, such as HTTP, FTP, SMTP, IMAP, etc.
TCP protocol uses the following special control information — so called flags:
•SYN (Synchronize) — connection initiation (first packet in each connection)
•ACK (Acknowledgement) — acknowledgement of received data
•RST (Reset) — request on termination of a current connection and on initiation of a new one
•URG (Urgent) — urgent packet
•PSH (Push) — request on immediate transmission of the data to upper TCP/IP layers
•FIN (Finalize) — connection finalization
