An attack was a hostile and forceful take on another individual or group. This individual or group were known as the attacker.
Due to the misunderstanding of a transmission from Captain Mitchell, a wrong story was told among the Novans for three generations. In this story, Humans attacked the Terra Nova colony and poisoned and gutted the adults. (ENT: "Terra Nova")
In June of 2151, the Andorian Imperial Guard Commander Thy'lek Shran expressed his concerns regarding a possible attack on his ship by Enterprise NX-01 when it leaves orbit of the planet with the Vulcan monastery at P'Jem. Sub-commander T'Pol instructed Enterprise to let his ship pass. (ENT: "The Andorian Incident")
Earth Cargo Service freighters were known to be attacked by Nausicaan pirates in a particular sector. In August of 2151, the ECS Fortunate was attacked by Nausicaan ships but the first officer Matthew Ryan was up for revenge and attacked the Nausicaans and their cargo base. (ENT: "Fortunate Son")