EntityQ649608· pop 11· linked from 9 articlesport knockingSign in to savesending a specific sequence of requests to closed ports to open a port on a firewallConnectionscomputer networkEntitycentral processing unitEntityIP addressEntitycryptographyEntitydigital object identifierEntityInternational Standard Serial NumberEntityInternet protocol suiteEntityfirewallEntityTransmission Control ProtocolEntityencryptionEntitydenial-of-service attackEntityUser Datagram ProtocolEntitySecure ShellEntityrootkitEntityInternet Control Message ProtocolEntitypacketEntitydaemonEntityportEntitynetwork securityEntitybrute-force attackEntityCategoriesInternet security