Obviously, there are always going to be fraudsters. The only thing you can really do about it is what we've always done, that is, setting up some kind of process to try and root them out, waiting for inconsistencies in their account and such, gaining evidence, and prosecuting them legally. The thing about these "we need to root out fraud NAO!!" campaigns is that they can often devolve into hysteria, hounding innocent people and putting unreasonable, overly broad restrictions in place that hurt more than they help.
And for what? You say there's a "trend", but can you actually validate that? Is there some new, recent outbreak of fraud? If so, we should identify what recent changes may have lead to it, and reform where appropriate. On the other hand, sometimes things like this just happen. Or, perhaps, you think it's always been the case that these programs are unusually susceptible to fraud, and you are using "trend" in that wishy washy, hyperbolic way that advocates often do (similar to how moral crusaders often thoughtlessly claim that teen suicides, drinking, drug use, etc... are "skyrocketing", as if it's beyond dispute, when in fact such things have been declining dramatically for decades). Then we can still take a rational approach. If fraud of government programs is higher than in private ones, then we should simply look at the differences in approaches being taken by both, and reform the governments approach to be in line with their (apparently) more successful one.
So, at the end of the day, the first thing we have to do is, at the very least get some basic statistics, study the issue from a broad view, and see if the level of fraud really is increasing, and really is above some reasonable level. If we simply say "fraud is a problem", well duh, it's something that's going to happen. The fact that it exists does not, in itself, necessitate extreme measures to combat it. The real question would be "is the rate of fraud above what we see in other programs", maybe "is there something we could do to maybe lower the rate for every program?", not "fraud exists, therefore we should take hysterical measures to combat the defrauding of one specific organization". And if we allow anecdotal evidence like "I saw fraudsters just the other day!" to guide our decision making, then we are are essentially setting the bar as low as possible. Perhaps you really did see a fraudster, OK, that's one case of fraud in one area, it does not establish a trend.
I suspect that any sort of broad movement of the sort you seem to be recommending would mostly just devolve into naked, hysterical vigilantism, with people intrusively attempting to identify people on disability in their area, following them around, seeing some event that they believe totally disproves whatever disability they are under the impression the recipient has (even though they don't have access to private information like that, and, in any case, aren't doctors and thus aren't qualified to make judgements about what qualifies as "disproving" their disability), and posting it on youtube with hysterical title, where a bunch of people see it, with the kindest and most humane commenters calling for summary drawing and quartering. Later, it turns out, the person who posted the video just didn't really know what they were talking about, and whatever the person was doing in the video really wasn't a disproof of their disability, but by that time people have moved on to other things, such as cat pictures. Things like this happen a few times, a few actual fraudsters may be caught, and many, many people on disability are harassed and hounded by hysterical individuals who are under the impression that being under disability should void any and all rights to privacy. Later, the whole thing blows over, as such things do, and does little to allay actual fraud, producing hugely disproportionate media attention and little else.