hdparm --read-sector returns data on a defective harddisk where dd would not.
However it turns out the data is from my computer (probably memory and thus a
possible security issue) and not the disk.

Sample:
 hdparm --verbose --read-sector 1001 /dev/sdb 
/dev/sdb:
reading sector 1001: oflags.lob_all=0xfc, flags={ nsect lbal lbam lbah dev
command }
oflags.hob_all=0xfc, flags={ nsect lbal lbam lbah }
using LBA48 taskfile
outgoing cdb:  85 09 0e 00 00 00 01 00 e9 00 03 00 00 e0 20 00
SG_IO: ATA_16 status=0x2, host_status=0x0, driver_status=0x8
SG_IO: sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 20 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00
incoming_data:  70 00 00 00 00 00 00 0a 00 00 00 00 00 00 00 00 00 00 00 00 28
1b 17 37 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 80 00 00 03 00 00
00 80 00 00 00 ff ff ff ff ff ff 90 f6 52 20 2f 6a 90 f6 52 20 2f 6a 70 3f 80
0d a8 08 2b 00 00 00 64 00 31 04 00 0b 47 72 65 67 65 72 2d 42 61 73 65 01 08
82 84 8b 96 0c 12 18 24 03 01 04 05 04 00 01 00 00 2a 01 00 30 14 01 00 00 0f
ac 04 01 00 00 0f ac 04 01 00 00 0f ac 02 00 00 32 04 30 48 60 6c dd 18 00 50
f2 02 01 01 86 00 03 a4 00 00 27 a4 00 00 42 43 5e 00 62 32 2f 00 dd 1e 00 90
4c 33 4e 10 1b ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 2d 1a 4e 10 1b ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 dd 1a 00 90 4c 34 04 05 1b 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 3d 16 04 05 1b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 dd 09 00 03 7f 01 01 00 00 ff 7f dd 0a 00 03 7f 04 01 00 06 00 40
00 c6 dd 9f e1 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ad 85 b1 0c d9
ef 28 62 a5 9e bc 3e 97 ae 0b 39 6c 19 c3 31 4b ff 87 8e ba 32 0f bd d7 95 c3
53 72 ba 58 a6 fd b7 f0 e7 69 fc 13 5f 8b bc 16 d6 59 c5 27 9b 03 d9 1c d9 a9
bf a7 22 d0 a8 5e 71 4d ed f8 2b ed e5 bc 67 c7 a3 bc 5c 5e 0f f3 b6
SG_IO: bad/missing sense data, sb[]:  70 00 05 00 00 00 00 0a 00 00 00 00 20 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
SG_IO: desc[]:  00 00
      ATA_16 stat=00 err=00 nsect=00 lbal=00 lbam=00 lbah=00 dev=00
succeeded