Due to and because of are direct synonyms. Both terms function as prepositions and mean that something was caused by something else.
Other synonyms that serve the same function and meaning are owing to, caused by, as a result of, by reason of, and on account of.
Because of is an older term than due to. According to Google’s ngram viewer the two terms are pretty even in their popularity and frequency of usage. After those two, which are the most used by far, the third most popular is a close tie between caused by and as a result of. As always, this data isn’t the most reliable since it is skewed toward the United States. But it is the best way to get a good view of phrase usage.
Be aware that due to is not spelled do to.
Chen said commercial banks would begin to implement the 40 per cent down payment for second-home buyers this month, down from the previous 70 per cent, which would accelerate sales of bigger and more expensive projects due to strong demand for upgrades. [South China Morning Post]
Angels right-hander Jered Weaver was placed on the 15-day disabled list because of left-hip inflammation and will undergo a series of medical tests, including an MRI, on Monday to determine the severity of the injury. [Los Angeles Times]
Authorities believe a power outage that left thousands of customers in the Witmann area sweltering was caused by an act of sabotage. [Arizona Daily Star]