Former Manchester City striker David Ball, making only his third start of the season, scored both goals - netting in the third and eighth minutes.
The win moves Posh to within three points of the automatic promotion places in League One, while the struggling Daggers have slipped into the bottom four.
Ferguson said: "It was a good result, the lads did everything I asked to the letter. We knew it would be a tough place to come and they throw bodies into the box. We dealt with it and there wasn't that many problems.
"Early doors Oliver Lee hit one across the face of the goal but then Bally (David Ball) scored two really good finishes and he has showed what he is all about.
"We have just seen it out in the end with a dogged, professional performance. But overall I`ve got to be pleased with a clean sheet and a victory. It was one we needed and sets us up lovely for Saturday."
Source: PA
Source: PA