Blues have conceded 42 goals in the top flight this season - the best record of the current bottom eight - ahead of Saturday's clash at Blackburn.
They have remained hard to break down despite losing key defender Scott Dann in January for the remainder of the campaign with a hamstring problem.
"If you look at some of the teams around us, you'd say they are pretty good at scoring goals," said Foster.
"But they haven't got what we've got at the back. As easily as those teams can score, they can ship goals as well.
"I think we've been pretty good at nicking the odd goal and grinding results out.
"It's what we are about in a way and our defensive record is one of the best of the teams in the bottom half of the table.
"Yes, we know we've got to score more goals and win more games. But hopefully that kind of record at the other end of the pitch will see us through as well."
Source: PA
Source: PA