That's a possibility. Having said this, I thought the current Jews in Israel were mostly from Eastern Europe?
Yes, but they don't originally come from that location and there was very little intermixing with the local population, so they usually looked foreign. If it they hadn't, it would have been easy to just move to a different city - or country even - and pretend they were Polish rather than Jewish during WW2. Yet this wasn't attempted. Their anatomical features are closer to those of Arabs than Eastern Europeans, so they actually stood out from the local crowd.
Intermixing still isn't popular today either, even in the multicultural west. For example,
82% of the population in England and Wales are white, but only
2.9% are of mixed background. And that's in a society where mixed couples are accepted, which wasn't the case in Eastern Europe in the previous centuries where religious differences were taken much more seriously than in the modern-day West.
Also, a it of anecdotal evidence, but I've lived in the UK for over 14 years now and somehow I can pick out Eastern Europeans from the crowd quite easily, especially the Polish, so there must be something about the facial features that makes us distinguishable.
My other counter argument is given how small and compact Gaza is and that inhabitants are in a prison I think it's safe to assume that people know people i.e. you are so and so from so and so family. It's not like people come in and out of the place. It's literally the same people who've been there for decades.
So, I don't know how IDF and Mossad can send in agents who embed themselves and rise to positions where they can influence the operations of Hamas. How long before someone asks - who are you? what's your family? where's your address? And does some digging.
It's not like fake papers or digital records will work when each person should be known by a whole web of other people given they've all been in that space for a while.
The population of Gaza is 2 million, with the overall Palestinian population being just below 5 million. I'd say it's quite hard to know everyone in a city of this size. My own hometown is around 140,000 people and although I was a very sociable person when I lived there, I certainly didn't know the majority of people living there. And that's with all the technology and freedom of movement available. With 50% unemployment in Gaza the inclination to move around is probably much lower. I can imagine that people in Gaza are much more suspicious of newcomers to their area, at the end of the day the name of that unit is on the internet, so it's probably known to them too. But I don't think Israeli agents just walk in and pretend to be Arabs. They surely must have a back-up story ready. I'd say impersonating a real person isn't out of question either.
Those are just my musings though, I can't find too many details online, but it's hard to expect any covert operations unit to share their tactics online.
What I can see is Hamas operatives can be blackmailed and bought out. Phones and computers can be hacked etc. Short term infiltration certainly can happen but an agent can't infiltrate long term without Mossad establishing some crazy multi generation roots for the agent inside Gaza.
From what I've found, that unit mostly infiltrates the civilian population, and usually on operation-by-operation basis rather than establishing multi-generational roots. Doing that would require the Israeli agents to be almost permanently based there, and I can't imagine they would be keen to do that.
And infiltrating a civilian population that cannot afford to be very mobile would be easier IMO.
As for infiltrating Hamas, according to
Sputnik International:
Hamas' precise troop force is unspecified, but various estimations have put the numerical strength of its service members at around 30,000 militants, if non-core members are summoned in an emergency.
Although mixing into a group of 30k people would be much harder, it wouldn't be entirely impossible. Especially if done on operation basis and with a good back-up story at hand.