Johannesburg: South Africa captain Faf du Plessis said today that he felt the 12-month ban on disgraced Australia skipper Steve Smith was "harsh".

He told a media conference in Johannesburg that he was "very sorry" for Smith and had texted him a message of support.

Smith and vice-captain David Warner were banned for 12 months and Cameroon Bancroft for nine months for attempted ball tampering during the third Test in Cape Town last Saturday.

The Australian cheating plot was foiled when TV cameras spotted Bancroft seeking to alter the condition of the ball with sandpaper.

Du Plessis, 33, was speaking on the eve of the fourth and final Test at the Wanderers of a drama-packed series in which South Africa hold a 2-1 lead. "It's been a crazy week. I have compassion for what he's going through.

"I think he's one of the good guys and he's just been caught in a bad place," said Du Plessis, who has twice been found guilty of ball tampering himself, but was only fined and never banned.

"I did send him a text. From a really deep place in my heart I feel for the guy. "I don't want to see guys going through that stuff.

"It's going to be incredibly hard for him over the next days so I sent him a message of support, saying he'll get through this and he must be strong."

Du Plessis said that although he regarded the bans imposed on Smith, Warner and Bancroft as harsh, he understood the context of the high values Australians expected from their cricket team.

Du Plessis welcomed the announcement by International Cricket Council chief executive Dave Richardson that there would be a review of the ICC code of conduct and penalties.

"I think it's overdue. All we ask for is consistency. There are a lot of grey areas," said Du Plessis, who was only made South Africa captain after being caught ball-tampering.

Despite his sympathy for Smith, Du Plessis said he and his team were determined to "finish the job".