Where does Yonatan Appel work?

Yonatan Appel is Co-founder, CTO of Upstream Security.

What companies did Yonatan Appel found?

Yonatan Appel founded Upstream Security.

Where did Yonatan Appel go to school?

Yonatan Appel studied at Tel Aviv University (Bachelor of Laws (LL.B.)); The Open University of Israel (Bachelor of Arts (B.A.), Computer Science).

Yonatan Appel

Founder

Co-founder, CTO at Upstream Security

Israel

FoundedUpstream Security

Find your path to Yonatan

345 people in our graph share verified history with Yonatan — schools, employers, funds. One of them is your warm intro.

Erik JohanssonunlockedYonatan: together at Upstream Security (2019–2026)

×5Yonatan: together at Upstream Security

×6Yonatan: together at Glilot Capital Partners

Co-founder, CTO at Upstream Security

Intro paths

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In turn, Yonatan can intro founders to Upstream Security's investors below.

Upstream Security's investors · 10

Alliance VenturesAmsterdam BMW i VenturesMountain View · $10M checks Cisco InvestmentsSan Jose Connect VenturesLos Angeles CRV (Charles River Ventures)Bay Area · $250K – $5M checks · since 2017 Glilot Capital PartnersHerzliya · $1.5M – $70M checks Maniv MobilityTel Aviv · $2M – $126M checks Roosh VenturesKiev · since 2026 Volvo Group Venture Capital ABGothenburg · $1.1M – $10.8M checks Y CombinatorSan Francisco · $500K checks · since 2026

Co-founders at Upstream Security

Yoav LevyCo-founder, CEO

Experience

Glilot Capital PartnersMembercurrent2019 — present
Upstream SecurityCo-Founder and CTOcurrent2016 — present
MicrosoftSenior Development Lead2009 — 2016
Israeli High-Tech CompaniesSecurity Consultant2009
ImpervaSenior Product Manager2006 — 2009

Skills & more

Network SecurityLeadership

From Yonatan's professional profile.

Frequently asked questions

Who is Yonatan Appel?: Co-founder, CTO at Upstream Security
Where does Yonatan Appel work?: Yonatan Appel is Co-founder, CTO of Upstream Security.
What companies did Yonatan Appel found?: Yonatan Appel founded Upstream Security.
Where did Yonatan Appel go to school?: Yonatan Appel studied at Tel Aviv University (Bachelor of Laws (LL.B.)); The Open University of Israel (Bachelor of Arts (B.A.), Computer Science).

Founder mafias

Tel Aviv University mafia377

Also came through, then founded or led a company.

Shlomo KramerBsc.Founded Check Point Software +2 Aviv EyalB.CSFounded Skillful +2 Shay HilelMBAFounded Biotax +2 Nir ZoharBSc. EE.Founded Chakratec +2 Eyal ShinarFounded Black Ore Technologies +1 Irit YanivMBAFounded Digma Medical +1

+ 370 more →

The Open University of Israel mafia57

Also came through, then founded or led a company.

Ilya SutskeverComputer ScienceFounded Safe Superintelligence +1 Ron GuraBachelor’s DegreeFounded Empathy Yan M.MathematicsFounded Aptos Orbital +1 Joseph SchneierBachelor of Fine Arts (B.F.A.)Founded Cinematic Health Education +1 Omer SadikaFounded Ika Interoperability +1 Shay FinkelsteinComputer Science and Business ManagementFounded Securitize

+ 50 more →

Imperva mafia16

Also came through, then founded or led a company.

Shlomo KramerCo-Founder, President & CEO (early years)Founded Check Point Software +1 Amichai ShulmanCo-Founder & CTOFounded Kanopy Security +1 Ryan WindhamVice President, Product & StrategyFounded AppViewX +1 Mark KraynakSVP & General Manager, Enterprise SolutionsFounded Early Rob WardBoard Observer (Co-Founder & Managing Director, Meritech Capital Partners)Founded Meritechcapital Patrick MassetAVP Sales NortheastFounded AIIM

+ 9 more →

Glilot Capital Partners mafia7

Also came through, then founded or led a company.

Tal MozesInvestorFounded Mitiga Ray RothrockMember of the Board of ExpertsFounded RedSeal Kobi SambourskyManaging PartnerFounded Mitiga Marcio LempertMemberFounded Red Access Ian AmitMember Of The Board Of AdvisorsFounded Gomboc Or ShoshaniMemberFounded Stream Security

Same school

Also attended Tel Aviv University795

Arnon DinurPartner at 83North Yoram SnirPartner at 83North Raz MaysharSenior Manager at Qualcomm Ventures David GoldschmidtManaging Director, Head of the Fund at Samsung Catalyst Fund Amit ShofarSr. Investment Director at Samsung Catalyst Fund Rutie AdarInvestments & Innovation Sr. Director, Israel at Samsung Catalyst Fund

+ 789 more

Also attended The Open University of Israel96

Ilya SutskeverCo-founder of OpenAI; co-founder & CEO of Safe Superintelligence Ron GuraCo-founder & CEO of Empathy Rutie AdarInvestments & Innovation Sr. Director, Israel at Samsung Catalyst Fund Shay FinkelsteinCTO & Co-founder at Collective Liquidity Lidia VerraBookkeeper at Triventures Adi GreenwaldAssociate at YL Ventures

+ 90 more

Shared employers

Also worked at Upstream Security18

Erik JohanssonInvestment Director at Volvo Group Venture Capital AB Kobi SambourskyCo-Founder and Managing Partner at Glilot Capital Partners Arik KleinsteinCo-Founder and Managing Partner at Glilot Capital Partners Kasper SageManaging Partner at BMW i Ventures Mike GranoffFounder and Managing Partner at Maniv Mobility Atanas MukovPartner at Walter Ventures

+ 12 more

Also worked at Microsoft2,000

Reid HoffmanCo-founder of LinkedIn; Partner at Greylock Garry TanPresident & CEO of Y Combinator Nat FriedmanCo-lead of Meta Superintelligence Labs; co-founder of NFDG Kai-Fu LeeChairman of Sinovation Ventures and CEO of 01.AI Bill GatesCo-founder of Microsoft; Chair of the Gates Foundation Mike KriegerCo-founder of Instagram; Chief Product Officer at Anthropic

+ 1,994 more

Also worked at Imperva29

Mark KraynakInvestor at Aspect Ventures Bill ButlerInvestor at Sand Hill Angels Rob WardCo-Founder and Partner at Meritech Capital Partners Patrick MassetCEO, AIIM at Vegvisir Capital Michael KantarovichInvestor at Cyberstarts Mickey BoodaeiPartner at Picture Capital

+ 23 more