The "@c0nvey" bot at twitter is used to flood twitter subjects with 1000's of repeats of the same tweets with different (often reportedly stolen) user names. The sheer volume makes it impossible at times to see (or even find) one's own tweets in a huge sea of identical tweets. Many of them include large images, making it even more difficult to see one's own tweets or tweets that weren't sent via "@c0nvey".
When one clicks on "block", only the apparent sender is offered to be blocked, not "@c0nvey".
The tweets are marked "user via @c0nvey".
This makes twitter useless for popular subjects, and twitter does not respond to complaints about @c0nvey, since it is a moneymaker for them.
Users of the @convey mechanism oftenappear to include groups supporting politicians running for election and companies trying to gain maximum exposure for a new product.
(Some politicians use it to make themselves appear more popular, but it's much more annoying than the bots that give the same politicians huge numbers of "fake followers" with the intent of encouraging others to "join the club")