Warner Bros. recently announced the cast and release date for the David Ayer-directed Suicide Squad movie, and now DC Entertainment Chief Creative Officer, Geoff Johns, appears to have tweeted the film's plot.
Ostrander's Suicide Squad (published for 66 issues from 1987-1992) is considered the modern take on the team, with Wiki describing it as:
The modern Suicide Squad (created by John Ostrander and Ryan Scott in the aforementioned Legends #3) is an antihero team of incarcerated supervillains who act as deniable assets for the United States government, undertaking high-risk black ops missions in exchange for commuted prison sentences. The group operates out of Belle Reve Penitentiary, under the directorship of Dr. Amanda Waller. The Suicide Squad's existence helps to explain why many convicted villains in the D.C. Universe roam free without having heroes tracking them down—until they, inevitably, attempt or commit another crime.
In addition, Ostrander's Suicide Squad also saw the team paired with another covert agency called Checkmate, which consisted of many different DC characters.
As the team is made of villains, other DC heroes and characters often played a part in the comic such as Batman attempting to take down the Suicide Squad only to have the team's government liaison, Amanda Waller, threaten to reveal Batman's identity if he didn't stop.
Likewise, Lois Lane has also investigated the Suicide Squad.
Per the title, the missions the team went on were considered suicide missions with both minor members and principal characters being killed off.