Recently, Turnitin was purchased for $1.75 billion dollars. Turnitin is the malicious corporation that neoliberal universities use to de-skill faculty labor. Ostensibly, it's to "reduce cheating", but -- as many have pointed out -- they do so in a simple-minded way that steals student work (everything students submit in the so-called "learning management systems" gets piratically stolen by the corporation and used to support their business model) and undermines the relationship between students and faculty. I use three strategies to reduce the incentives and potential for student cheating without Turnitin.
My primary goal is to have each student or group do novel projects. If work is actually novel, there are no easy candidates to cheat from. If each student (or group) is working on something unique, they can collaborate and share resources without the potential for competition or cheating to come into play. If you have students all working on identical papers (or solving "classic" problems) there is always a tempting array of examples of the "work" already done (and probably done better than any student could do it).
Second, I have students do their work in an environment where I can see the the development of the project over time. I used to use a Wiki or Drupal Revisions for this. Currently, I'm using Google Docs. This way, I can see snapshots of the project from inception to outline to finished document. I can provide feedback along the way and, in the end, have great confidence that the finished product was the authentic work of the student(s) -- much more so than if the document sprang into existence the night before it was due.
Finally, I aim to have students work on projects that are genuinely engaging. If students do authentic work that they see as valuable, there's no incentive to cheat: students will do the work because it's real work that has intrinsic merit to them.
The only reason for something like "Turnitin" is that we've created an environment where faculty have too many students to get to know them all personally. Neoliberal universities are constantly reducing the number of faculty, increasing their workload, and substituting robot labor like "Turnitin" to allowing faculty to know their students well enough to offer meaningful work and guide their writing personally. Faculty should resist the speed-up and opt-out of having their students' submissions be stolen by the parasitic corporations that aim to create a hostile environment for everyone.