| K053 | K0ad K1d | K-159 |
| K1LL3r B0y | K1n9k0ng | K1P0D |
| K1tk4t | K2 | K3m4n9i |
| K3vin Mitnick | K3xji | K4cp3r & Ablus |
| K4k4shi | K4m1k451 | K4P0 |
| K8gege | K-9999 | Ka0x |
| Kaan KAMIS | KaBuS | Kacak |
| Kacper | Kacper Szczesniak | Kacper Szurek |
| Kaczinski Ramirez | Kad | KaDaL-X |
| Kadokev | Kagan Capar | Kagan Eglence |
| Kağan EĞLENCE | KaGra | KAhara MAnhara |
| Kahir | KaHPeSeSe | Kahvi-0 |
| KaiJern Lau | Kailash Bohara | Kaimi |
| Kaiqu Chen | Kallimero | Kalou |
| Kaloyan Olegov Georgiev | Kamaljeet Kumar | Kamil Brenski |
| Kamil Frankowicz | Kamil Sienicki | Kamil Suska |
| KaMtiEz | Kanatoko | Kaneda |
| Kanedaaa | Kang | KAPDA |
| Karak0rsan | Karar Alshami | Karb0nOxyde |
| Karimo DM | Karma | Karn Ganeshen |
| Karol | Karol Wiesek | Karsten Konig |
| KaRTaL | Karthik R | Karthik UJ |
| Kashinath T | Kaslov Dmitri | Kasper Karlsson |
| Katatafish | Katharsis | Kaushal Desai |
| Kaustubh G. Padwad | Kay Roepke | Kazza |
| KBA At Sogeti Esec | Kc | K-C0d3r |
| Kc57 | Kcope | K.C. Wong |
| KedAns-Dz | Keelis | KeenTeam |
| Keerati T. | Kees Cook | Kefka |
| Keita Yamaguchi | Keith Lee | Keith McCanless |
| Keith Thome | Keith Woodworth | Ke Liu |
| Kelly Correll | Kelvin Yip | Kender.Security |
| Kendrick Lam | Ken Farnen | Ken@FTU |
| Ken Hollis | Keniobats | Ken Millar |
| Kenneth Belva | Kenneth F. Belva | Kenney Lu |
| Kenny Mathis | Keracker | Kerb |
| Kerem125 | Kerem Kocaer | Kernel-32 |
| Kernel Panik | Kerry Enfinger | Kestutis Gudinavicius |
| Kevin | Kevin Cernekee | Kevin Fenzi |
| Kevin Finisterre | Kevin Joensen | Kevin Kirsche |
| Kevin Locati | Kevin L Prigge | Kevin McGuigan |
| Kevin Randall | Kevork Belian | Key |
| KeyCoder | Key Night | Keyser Soze |
| Kezzap66345 | Kf | K. Gudinavicius |
| Khal4n1 | Khaled Salem | Khalil Bijjou |
| Khalsa | Khashayar Fereidani | Khc@bsdmail.org |
| Khoaimi | Kian.mohageri | Kiba |
| Kiborg | Kicktd | KiDebug |
| Kiki | Kikkert Security | Kil13r |
| Kil3r | Kil3r Of Lam3rZ | Kill-9 |
| Kill9 | Killall-9 | Killprog.org |
| KIM | KIM Kee-hong | Kim Yong-jun |
| KimYongJun | Kingcope | Kingcope |
| KinG-LioN | KinG Of PiraTeS | KingOfSka |
| KiNgOfThEwOrLd | Kingpin | King Purba |
| KINGSABRI | KingSkrupellos | KinSize |
| Kiran Ghimire | Kire Bozorge Khavarmian | Kirk Corey |
| Kistler Ueli | Kitchaphan Singchai | Kit Knox |
| Kivson | Kjetil Kjernsmo | K. K. Mookhey |
| Kkr | Kl3 GMjq6 | Klaus Eisentraut |
| Klaus Heckelmann | Klayton Monroe | Klepto |
| Klikki | Klinza | Kmkz |
| Knight4vn | Knight Commander | KnocKout |
| Knud | Knud & NSense | Knud Erik Højgaard |
| Knud Erik Hjgaard | Knud Erik Hojgaard | Knull |
| Knxone | Koby | Koczkatamas |
| KoF2002 | Koh You Liang | Koi8-r Shelz |
| Kokanin | Kokn3t | Kold |
| Koller | Kolya5544 | Komrade |
| K-one | Konrad Malewski | Konstantin Boldyshev |
| Konstantin Burov | Konstantin Kolinko | Konstantinos Alexiou |
| Konstantin Preisser | Konstantin V. Gavrilenko | Koray |
| KoreLogic | Korpritzombie | KorsaN |
| Korty | Koshi | Kostya Kortchinsky |
| Kostya KORTCHINSKY | K-otik | Kousuke Ebihara |
| Kozan | Kr0ff | Krad Chad |
| Krafty | Krahmer | KraL BeNiM |
| Kralor | Krastanoel | Krasza |
| KrazySnake | Kre0n | Kripthor |
| Krishna Vamshi Katta Rokkaiah | Krishna Yadav | Krishna Yadavu |
| Krish Pandey | Kris Kennaway | Kris Kubicki |
| Kristian Erik Hermansen | Kristian Hermansen | Kristian Koehntopp |
| Kristoffer Brånemyr | Krit | Krochos |
| Krusty Hack | Kryptos Logic | Krystian Kloskowski |
| Krzysztof Burghardt | Krzysztof Kotowicz | Ksa Ksa82 |
| Ksecurity | K'sOSe | Kspecial |
| K-sPecial | KSR[T] | Ktha |
| Ktha@hushmail.com | Kubilay Onur Gungor | Kumar Saurav |
| Kundera | Kuon | KuRaK |
| Kurdish Hackers Team | Kurdish Security | Kurd-Team |
| Kuroi'SH | Kurt Seifried | Kusol Watchara-Apanukorn |
| Kutas | Kv1to | Kw3[R]Ln |
| Kyhvedn | Kyle Lovett | Kyle Neideck |
| Kyle Quest | Kyong-won Cho | Kyprizel |
| Kyriakos Economou | Kyuzo | Kzar |
Vulmon