In-band　Network　Telemetry　(INT)　is　a　widely　used　monitoring　framework　in　modern　large-scale　networks　that　provides　fine-grained　visibility　into　network　conditions　by　inserting　telemetry　data　into　packets.　However,　this　mechanism　also　introduces　new　vulnerabilities　that　malicious　attackers　can　exploit.　In　this　paper,　we　present　four　In-band　Network　Telemetry　Manipulation　Attacks　that　take　advantage　of　INT＇s　weakness,　demonstrating　that　attackers　can　cause　severe　damage　with　little　effort　by　manipulating　INT　packets.　To　address　this　issue,　we　design　SecureINT,　a　novel　INT　prototype　that　ensures　confidentiality　and　integrity　for　INT　packets.　To　meet　the　stringent　computational　requirements　of　programmable　switches,　we　comprehensively　analyze　possible　attacks　on　the　deployed　encryption/hash　algorithms　and　modify　them　accordingly　without　compromising　their　security.　According　to　the　experiments,　SecureINT　can　be　deployed　on　programmable　switches　using　a　single　pipeline,　providing　encryption　and　integrity　verification　for　INT　packets　with　minimal　overhead.　©　2023　IEEE.