Not surprised at all.
These coding contract sites provide a high percentage of the spammers on Yahoo! Answers, where I run a spam destruction group. An estimated 5% of all answers posted are spam, about 10,000 posts a day, impossible to filter because of their varied (and constantly changing) content.
Freelancer.com is the first site I check every few weeks, looking for job offers for spammers. They are described as on-line data entry, and some go into a lot of detail how the accounts are to be set up and used, in order to avoid looking like spam. But they want hundreds of posts of their links.
This "work" pays from 2c to 10c per post, counting only those that survive being filtered or reported off the site. The smarter contractors use bots (which are also advertised, either for sale, or as contracts for writing them). The poorer ones, in the third world, do it in family teams, all by hand.
Requests to rewrite articles in different ways, or to provide lists of synonyms (to be used for varying a given text) would also be from spammers, hoping to avoid being caught it there is a filter for commonly used phrases. This way they also hope to make their spam look like genuine replies. (The best spam fighting tool is an experienced person with a good eye; what they see in a single post to ID it as spam is virtually impossible to teach to a software program).
Knowing what contracts are being offered sometimes tells us what to look out for. Concentrated campaigns to remove them all at once reduces the spammers' incomes enough to make them give up. The really successful long-term ones appear to be wages employees, who are not deterred by most of their content being immediately removed. They are mostly for phishing sites that make enough to keep people on the payroll.
I'm not surprised to see malware-writing contracts on these sites. A good 40% of their offerings don't look totally legal, and 95% are substantially underpaid for the work involved/ They attract mostly desperate people in poor countries, who may not be aware of the legal status of the work being offered.