The 50-year-old Dunga, who captained Brazil to their fourth world 
title in 1994, was last in charge of the national team in 2010 when he 
was sacked for failing to take them further than the World Cup 
quarter-finals in South Africa.
"I am immensely happy to be back," he told reporters.
"I
 have an outline of what I want. Fans know me and they know I am not 
going to sell a dream but a reality and that reality is we have to work 
hard."
Dunga acknowledged Brazil have fallen behind the leading 
European teams in recent years and said he has spent his time outside 
football watching games and talking to managers and former players such 
as Arsene Wenger, Ruud Gullit and Arrigo Sacchi.
He warned fans not to expect cavalier football and said the best form of attack is defence.
"Managers
 today organise the defence in order to be able to attack," he told 
reporters at a news conference to announce his appointment. "The 
important thing is not to have four or five players up front, it is to 
get forward with four or five players. Football today is total. Everyone
 needs to participate."
Dunga played for a host of clubs in 
Brazil, Italy, Germany and Japan and was known for his combative 
midfield style. He captained Brazil to their fourth World Cup in the 
United States in 1994.
First Appointment
He
 was first appointed Brazil manager in 2006 but although he won both the
 2007 Copa America and the 2009 Confederations Cup, his team crumbled 
when they went behind to the Netherlands at the 2010 World Cup and lost 
2-1, costing him his job.
His only managerial position in the 
years since was a 10-month spell in charge of Internacional, the club 
where he started and ended his playing career.
His appointment as the new Brazil boss was leaked last week and comes just 10 days after Germany won the World Cup.
Brazil
 hosted the tournament and were favourites to lift the trophy for a 
record sixth time. But the way they were outfoxed by faster, more agile 
and tactically astute teams brought calls for a revolution in Brazilian 
football. Some critics called for a foreign manager to be appointed and 
others wanted a complete overhaul of the Brazilian Football 
Confederation (CBF).
However, the CBF did not wait to dissect the 
defeats and two days after the cup ended they appointed former 
goalkeeper and player agent Gilmar Rinaldi as technical coordinator in 
charge of all Brazil's adult, youth and female sides.
Rinaldi is 
from the south of the country like Dunga and the two were friends and 
team mates at both Internacional and on the Brazil side that won the 
1994 World Cup. Their friendship and ability to work together is 
considered to be a major factor in Dunga's appointment just days after 
Rinaldi was chosen out of the blue.
Dunga acknowledged he has his work cut out to win over fans, with online polls showing a large majority against his appointment.
"The
 fans are hurting," he said, citing Nelson Mandela as a man whose 
patience was rewarded. "I need to look for support of the 20-odd percent
 who support me and try to win over the 70-odd percent who don't with 
hard work and commitment."
Dunga's first match in charge will be 
against Colombia in Miami in early September, with further friendlies 
against Ecuador, Argentina and Turkey to follow.
His first competitive fixtures will be in next year's Copa America in Chile.